next solver: provisional cache

[lcnr]

this adds the cache removed in #115843. However, it should now correctly track whether a provisional result depends on an inductive or coinductive stack.

While working on this, I was using the following doc: https://hackmd.io/VsQPjW3wSTGUSlmgwrDKOA. I don't think it's too helpful to understanding this, but am somewhat hopeful that the inline comments are more useful.

There are quite a few future perf improvements here. Given that this is already very involved I don't believe it is worth it (for now). While working on this PR one of my few attempts to significantly improve perf ended up being unsound again because I was not careful enough ✨

r? @compiler-errors

[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 core trait solver

cc @rust-lang/initiative-trait-system-refactor

[compiler-errors]

🙈

@bors r+ rollup (new solver only)

[bors]

📌 Commit 13aa900 has been approved by compiler-errors

It is now in the queue for this repository.

[bors]

⌛ Testing commit 13aa900 with merge 2b1365b...

[bors]

☀️ Test successful - checks-actions
Approved by: compiler-errors
Pushing 2b1365b to master...

[rust-timer]

Finished benchmarking commit (2b1365b): 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)	1.3%	[1.3%, 1.3%]	1
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-1.1%	[-1.1%, -1.1%]	1
All ❌✅ (primary)	1.3%	[1.3%, 1.3%]	1

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)	0.9%	[0.5%, 1.8%]	4
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	0.9%	[0.5%, 1.8%]	4

Binary size

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

Bootstrap: 666.39s -> 666.917s (0.08%)
Artifact size: 308.38 MiB -> 308.37 MiB (-0.00%)