Port high resolution local SDFs

[ChrisLoer]

Launch Checklist

This PR brings gl-js to parity with gl-native by porting the 2x resolution local glyph generation. It includes:

• 2x resolution local glyphs
• Glyph metrics extraction via TextMetrics and support for local generation of non-ideographic glyphs using localFontFamily map option. (Previously in PR Add 'localFontFamily' option to support rendering of all glyphs. #10267: I've rolled it into this PR because both PRs depend on the same TinySDF changes and I've been testing them together).
• Performance optimizations to offset the cost of doubling the SDF resolution: mainly (1) don't double-generate glyphs that share the same font and (2) trim whitespace from glyphs.

The visual improvement is noticeable on high DPI screens, and can also be seen easily in large labels:

Before

After

For default settings, these changes have negligible performance impact for maps without heavy CJK-use. For CJK maps, the main impact is at load time (generating SDFs for the first time), although there is a small ongoing hit from loading larger glyph atlases (SDF generation is also an ongoing cost once the map is loaded, but the rate of new glyph generation drops off pretty quickly once a set of common characters are loaded). One option we have for ameliorating the load time performance hit is to do SDF generation on the workers. However, if we can get away with it, I'd like to avoid that complexity. For performance testing, I used benchmap-js with a Japanese-language style that rendered three cities at z8, z12, and z16. The main results were:

Full load: 160ms/16% slower
Speed index: 96ms/19% slower
FPS: -6.3
Jank: indeterminate
Dropped frames: 7 greater

The 16% full-load slow down is similar to the performance hit we accepted on the "Tokyo All Local Glyphs" perf benchmark on the native side.

• briefly describe the changes in this PR
• include before/after visuals or gifs if this PR includes visual changes
• write tests for all new functionality
• document any changes to public APIs
• post benchmark scores
• manually test the debug page
• tagged @mapbox/map-design-team @mapbox/static-apis if this PR includes style spec API or visual changes
• tagged @mapbox/gl-native if this PR includes shader changes or needs a native port
• apply changelog label ('bug', 'feature', 'docs', etc) or use the label 'skip changelog'
• add an entry inside this element for inclusion in the mapbox-gl-js changelog:

<changelog>
- Add `localFontFamily` map option that enables local generation of all font glyphs
- Introduce high resolution local glyph generation for improved rendering quality of glyphs generated using `localIdeographFontFamily` or `localFontFamily` options
</changelog>

cc @mourner @zmiao @asheemmamoowala @alexshalamov @YoshiYazawa @tsuz @ansis

[mourner]

This looks great! Added a few nits. Perhaps also worth adding some code comments around heuristics like baselineAdjustment.

[ChrisLoer]

Some belated testing with Arabic text turned up what look like some alignment issues:

Server side glyphs

Locally generated glyphs

The locally generated text is legible, but there are some improperly overlapping glyphs.