TokenMap -> SpanMap rewrite

[Veykril]

Opening early so I can have an overview over the full diff more easily, still very unfinished and lots of work to be done.

The gist of what this PR does is move away from assigning IDs to tokens in arguments and expansions and instead gives the subtrees the text ranges they are sourced from (made relative to some item for incrementality). This means we now only have a single map per expension, opposed to map for expansion and arguments.

A few of the things that are not done yet (in arbitrary order):

• generally clean up the current mess
• proc-macros, have been completely ignored so far
• syntax fixups, has been commented out for the time being needs to be rewritten on top of some marker SyntaxContextId
• macro invocation syntax contexts are not properly passed around yet, so $crate hygiene does not work in all cases (but most)
  • builtin macros do not set spans properly, $crate basically does not work with them rn (which we use)
    - [ ] remove all uses of dummy spans (or if that does not work, change the dummy entries for dummy spans so that tests will not silently pass due to havin a file id for the dummy file)
  • de-queryfy macro_expand, the sole caller of it is parse_macro_expansion, and both of these are lru-cached with the same limit so having it be a query is pointless
• fix eager macro spans and other stuff
  • simplify include! handling
• Figure out how to undo the sudden () expression wrapping in expansions / alternatively prioritize getting invisible delimiters working again
• Simplify InFile stuff and HirFIleId extensions
  - [ ] span crate containing all the file ids, span stuff, ast ids. Then remove the dependency injection generics from tt and mbe

Fixes #10300
Fixes #15685

[Veykril]

Okay this is ready now, so we can merge this after tomorrows release, and depending on the fallout we might want to skip the following stable release, though I don't expect this to be that problematic.

[lnicola]

@bors r+

[bors]

📋 Looks like this PR is still in progress, ignoring approval.

Hint: Remove [WIP] from this PR's title when it is ready for review.

[lnicola]

@bors retry

[lnicola]

@bors r+

[bors]

📌 Commit 18f1a3c has been approved by lnicola

It is now in the queue for this repository.

[bors]

⌛ Testing commit 18f1a3c with merge e91fdf7...

[bors]

☀️ Test successful - checks-actions
Approved by: lnicola
Pushing e91fdf7 to master...

[Veykril]

This also seemed to have a decent improvement on body lowering time? Not quite sure why though

[lnicola]

(sorry for the duplicate ping, I'm not sure how well they work in commit comments)

@Veykril is this supposed to be cfg!(debug_assertions) or can we call it unconditionally?

[Veykril]

it was supposed do be debug_assertions (cause it may reallocate unnecessarily)