Remove fold code and add Const::internal() to StableMIR

[celinval]

We are not planning to support user generated constant in the foreseeable future, so we are cleaning up the fold logic and user created type for now. Users should use Instance::resolve in order to trigger monomorphization.

The Instance::resolve was however incomplete, since we weren't handling internalizing constants yet. Thus, I added that.

I decided to keep the Const fields private in case we decide to translate them lazily.

[rustbot]

r? @davidtwco

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[rustbot]

This PR changes Stable MIR

cc @oli-obk, @celinval, @spastorino, @ouz-a

[celinval]

r? @oli-obk

[oli-obk]

This can now be an IndexMap, too

[oli-obk]

@bors delegate+

r=me with types made an IndexMap

[bors]

✌️ @celinval, you can now approve this pull request!

If @oli-obk told you to "r=me" after making some further change, please make that change, then do @bors r=@oli-obk

[celinval]

@bors r=@oli-obk

[bors]

📌 Commit cf6a04e has been approved by oli-obk

It is now in the queue for this repository.

[bors]

☔ The latest upstream changes (presumably #117135) made this pull request unmergeable. Please resolve the merge conflicts.

[celinval]

@bors r=@oli-obk

[bors]

📌 Commit 17f6df9 has been approved by oli-obk

It is now in the queue for this repository.

[bors]

⌛ Testing commit 17f6df9 with merge b66fe58...

[bors]

☀️ Test successful - checks-actions
Approved by: oli-obk
Pushing b66fe58 to master...

[rust-timer]

Finished benchmarking commit (b66fe58): 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)	-	-	0
Improvements ✅ (primary)	-0.6%	[-0.6%, -0.6%]	1
Improvements ✅ (secondary)	-3.4%	[-3.4%, -3.4%]	1
All ❌✅ (primary)	-0.6%	[-0.6%, -0.6%]	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
Regressions ❌ (secondary)	2.3%	[2.3%, 2.3%]	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: missing data
Artifact size: 304.40 MiB -> 304.42 MiB (0.01%)