Move predicate, region, and const stuff into their own modules in middle

[compiler-errors]

This PR mostly moves things around, and in a few cases adds some ty:: to the beginning of names to avoid one-off imports.

I don't mean this to be the most thorough move/refactor. I just generally wanted to begin to split up ty/mod.rs and ty/sty.rs which are huge and hard to distinguish, and have a lot of non-ty stuff in them.

r? lcnr

[lcnr]

@bors r+ rollup=never p=1

[bors]

📌 Commit 233b213 has been approved by lcnr

It is now in the queue for this repository.

[bors]

⌛ Testing commit 233b213 with merge b3a4636...

[bors]

💥 Test timed out

[rust-log-analyzer]

A job failed! Check out the build log: (web) (plain)

Click to see the possible cause of the failure (guessed by this bot)

[compiler-errors]

@bors retry

[bors]

⌛ Testing commit 233b213 with merge 991a9dc...

[bors]

☀️ Test successful - checks-actions
Approved by: lcnr
Pushing 991a9dc to master...

[rust-timer]

Finished benchmarking commit (991a9dc): 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)	2.3%	[2.0%, 3.2%]	6
Regressions ❌ (secondary)	2.0%	[0.7%, 3.4%]	4
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	2.3%	[2.0%, 3.2%]	6

Cycles

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)	5.3%	[5.3%, 5.3%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-	-	0

Binary size

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

Bootstrap: 660.723s -> 663.211s (0.38%)
Artifact size: 308.07 MiB -> 308.09 MiB (0.01%)