Rewrite AtlasEngine to allow arbitrary overhangs (#14959)

This is practically a from scratch rewrite of AtlasEngine.

The initial approach used a very classic monospace text renderer, where
the viewport is subdivided into cells and each cell is assigned one
glyph texture, just like how real terminals used to work.
While we knew that it would have problems with overly large glyphs,
like those found in less often used languages, we didn't expect the
absolutely massive number of fonts that this approach would break.
For one, the assumption that monospace fonts are actually mostly
monospace has turned out to be a complete lie and we can't force users
to use better designed fonts. But more importantly, we can't just
design an entire Unicode fallback font collection from scratch where
every major glyph is monospace either. This is especially problematic
for vertical overhangs which are extremely difficult to handle in a
way that outperforms the much simpler alternative approach:
Just implementing a bog-standard, modern, quad-based text renderer.

Such an approach is both, less code and runs faster due to a less
complex CPU-side. The text shaping engine (in our case DirectWrite)
has to resolve text into glyph indices anyways, so using them directly
for text rendering allows reduces the effort of turning it back into
text ranges and hashing those. It's memory overhead is also reduced,
because we can now break up long ligatures into their individual glyphs.
Especially on AMD APUs I found this approach to run much faster.

A list of issues I think are either obsolete (and could be closed)
or resolved with this PR in combination with #14255:

Closes #6864
Closes #6974
Closes #8993
Closes #9940
Closes #10128
Closes #12537
Closes #13064
Closes #13527
Closes #13662
Closes #13700
Closes #13989
Closes #14022
Closes #14057
Closes #14094
Closes #14098
Closes #14117
Closes #14533
Closes #14877

## PR Checklist
* Enabling software rendering enables D2D mode ✅
* Both D2D and D3D:
  * Background appears correctly ✅✅
  * Text appears correctly
    * Cascadia Code Regular ✅✅
    * Cascadia Code Bold ✅✅
    * Cascadia Code Italic ✅✅
    * Cascadia Code block chars leave (almost) no gaps ✅✅
    * Terminus TTF at 13.5pt leaves no gaps between block chars ✅✅
    * ``"`u{e0b2}`u{e0b0}"`` in Fira Code Nerd Font forms a square ✅✅
  * Cursor appears correctly
    * Legacy small/medium/large ✅✅
    * Vertical bar ✅✅
    * Underscore ✅✅
    * Empty box ✅✅
    * Full box ✅✅
    * Double underscore ✅✅
  * Changing the cursor color works ✅✅
  * Selection appears correctly ✅✅
  * Scrolling in various manners always renders correctly ✅✅
  * Changing the text antialising mode works ✅✅
  * Semi-transparent backgrounds work ✅✅
  * Scroll-zooming the font size works ✅✅
  * Double-size characters work ✅✅
  * Resizing while text is printing works ✅✅
  * DWM `+Heatmap_ShowDirtyRegions` shows that only the cursor
    region is dirty when it's blinking ✅✅
* D2D
  * Margins are filled with background color ❌
    They're filled with the neighboring's cell background color for
    convenience, as D2D doesn't support `D3D11_TEXTURE_ADDRESS_BORDER`
* D3D
  * Margins are filled with background color ✅
  * Soft fonts work ✅
  * Custom shaders enable continous redraw if time constant is used ✅
  * Retro shader appears correctly ✅
  * Resizing while a custom shader is running works ✅

.github/actions/spelling/allow/apis.txt

@@ -214,6 +214,7 @@ userenv
 USEROBJECTFLAGS
 Viewbox
 virtualalloc
+vsnwprintf
 wcsstr
 wcstoui
 WDJ

.github/actions/spelling/expect/expect.txt

@@ -1784,6 +1784,7 @@ STARTWPARMS
 STARTWPARMSA
 STARTWPARMSW
 Statusline
+stb
 stdafx
 STDAPI
 stdc

NOTICE.md

@@ -276,6 +276,31 @@ OTHER DEALINGS IN THE SOFTWARE.
 For more information, please refer to <http://unlicense.org/>
 ```
 
+## stb
+
+**Source**: [https://github.com/nothings/stb](https://github.com/nothings/stb)
+
+### License
+
+```
+This is free and unencumbered software released into the public domain.
+Anyone is free to copy, modify, publish, use, compile, sell, or distribute this
+software, either in source code form or as a compiled binary, for any purpose,
+commercial or non-commercial, and by any means.
+In jurisdictions that recognize copyright laws, the author or authors of this
+software dedicate any and all copyright interest in the software to the public
+domain. We make this dedication for the benefit of the public at large and to
+the detriment of our heirs and successors. We intend this dedication to be an
+overt act of relinquishment in perpetuity of all present and future rights to
+this software under copyright law.
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+```
+
 ## ConEmu
 **Source**: [https://github.com/Maximus5/ConEmu](https://github.com/Maximus5/ConEmu)
 

oss/stb/LICENSE

@@ -0,0 +1,37 @@
+This software is available under 2 licenses -- choose whichever you prefer.
+------------------------------------------------------------------------------
+ALTERNATIVE A - MIT License
+Copyright (c) 2017 Sean Barrett
+Permission is hereby granted, free of charge, to any person obtaining a copy of
+this software and associated documentation files (the "Software"), to deal in
+the Software without restriction, including without limitation the rights to
+use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
+of the Software, and to permit persons to whom the Software is furnished to do
+so, subject to the following conditions:
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
+------------------------------------------------------------------------------
+ALTERNATIVE B - Public Domain (www.unlicense.org)
+This is free and unencumbered software released into the public domain.
+Anyone is free to copy, modify, publish, use, compile, sell, or distribute this
+software, either in source code form or as a compiled binary, for any purpose,
+commercial or non-commercial, and by any means.
+In jurisdictions that recognize copyright laws, the author or authors of this
+software dedicate any and all copyright interest in the software to the public
+domain. We make this dedication for the benefit of the public at large and to
+the detriment of our heirs and successors. We intend this dedication to be an
+overt act of relinquishment in perpetuity of all present and future rights to
+this software under copyright law.
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

oss/stb/MAINTAINER_README.md

@@ -0,0 +1,4 @@
+### Notes for Future Maintainers
+
+Search for files prefixed with `stb_` in this project.
+At the time of writing, the only file being used is `stb_rect_pack.h`.

oss/stb/cgmanifest.json

@@ -0,0 +1,15 @@
+{
+  "$schema": "https://json.schemastore.org/component-detection-manifest.json",
+  "Registrations": [
+    {
+      "component": {
+        "type": "git",
+        "git": {
+          "repositoryUrl": "https://github.com/nothings/stb",
+          "commitHash": "5736b15f7ea0ffb08dd38af21067c314d6a3aae9"
+        }
+      }
+    }
+  ],
+  "Version": 1
+}