Restructure rustc_type_ir a bit

[compiler-errors]

1. Split sty into new ty_kind/region_kind/const_kind modules, so that when we uplift more kinds (e.g. PredicateKind, ClauseKind, and ExistentialPredicate), they can live in their own simple-to-understand files.
2. Split up the structural_impls module, which is a kitchen sink of random impls -- move TypeFoldable and TypeVisitable impls into existing fold and visit modules, respectively.
3. Move the DebugWithInfcx trait and blanket impls into a new debug module, and TypeFlags definition into a new flags module.
4. Move Interner trait into a new interner module. I expect this file to get a lot larger as we make the interner more powerful for the trait solver refactor.

r? @ghost for now, will assign once #116946 lands

[rustbot]

These commits modify the Cargo.lock file. Unintentional changes to Cargo.lock can be introduced when switching branches and rebasing PRs.

If this was unintentional then you should revert the changes before this PR is merged.
Otherwise, you can ignore this comment.

Some changes occurred to the CTFE / Miri engine

cc @rust-lang/miri

[jackh726]

@bors r+

nice cleanups

[bors]

📌 Commit c3fd438 has been approved by jackh726

It is now in the queue for this repository.

[bors]

⌛ Testing commit c3fd438 with merge 96027d9...

[bors]

☀️ Test successful - checks-actions
Approved by: jackh726
Pushing 96027d9 to master...

[rust-timer]

Finished benchmarking commit (96027d9): comparison URL.

Overall result: no relevant changes - no action needed

@rustbot label: -perf-regression

Instruction count

This benchmark run did not return any relevant results for this metric.

Max RSS (memory usage)

Results

This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	3.9%	[3.9%, 3.9%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-	-	0

Cycles

This benchmark run did not return any relevant results for this metric.

Binary size

This benchmark run did not return any relevant results for this metric.

Bootstrap: 630.346s -> 631.391s (0.17%)
Artifact size: 304.04 MiB -> 304.06 MiB (0.01%)