feat: Unroll loops iteratively

[sirasistant]

Description

Problem*

Resolves #4736

Summary*

Instead of trying to unroll loops once, adds a meta pass that tries to unroll as many times as necessary, simplifying and doing mem2reg between unrolls.

• For the cases where the program unrolls succesfully at the first try, no compile time overhead is created
• For the cases where the program does contain an unknown at compile time loop bound, it'll try one more time before failing, since the stop condition is that "this unroll retry generated the same amount of errors as the previous one"
• For the cases where the program doesn't contain an unknown at compile time loop bound, instead of failing it'll do as many unrolls as necessary to unroll the loop.

Additional Context

Documentation*

Check one:

• No documentation needed.
• Documentation included in this PR.
• [For Experimental Features] Documentation to be submitted in a separate PR.

PR Checklist*

• I have tested the changes locally.
• I have formatted the changes with Prettier and/or cargo fmt on default settings.

[jfecher]

Looks good, just some nitpicks

[jfecher]

LGTM

Only doing the additional passes on error fixes my main concern about doing such extra passes before this PR

[jfecher]

New changes LGTM. A bit unfortunate that mem2reg needs to be spammed a bit - this is a consequence of it never being able to be "perfect" I think since the pass is undecidable in general. Since this is only done on functions that fail to unroll though I think it should have minimal perf impact and should be fine.