Change reachability module to use StableMIR

[celinval]

Rewrite the reachability module to use Stable APIs wherever possible. Note that in StableMIR the instance body is already monomorphized and constants are already evaluated, which simplifies the code for most of it, except to handle stubbing issue #2589.

For the stubbing issue, we still use a mix of stable and internal APIs to detect an invalid monomorphization.

Call-outs

1. This change requires the newest version of the Rust toolchain. Thus, it is upgrading the version as well.
2. Creating this as a draft until Fix smir's Ty::Ref pretty printing rust-lang/rust#118274 is merged.
3. I ran s2n-quic manually to assess performance and no significant difference.

• s2n-quic-core: 36.86 vs 37.19
• s2n-quic-platform: 16.17 vs 16.19

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 and MIT licenses.

[adpaco]

It's looking really good. I wonder if we could add links to the stable MIR project or its APIs so it's clear what's going on here. But I'm not sure how much you'll use these APIs in other parts of the compiler, maybe it's better to add that elsewhere.

[zhassan-aws]

I wonder if we could add links to the stable MIR project or its APIs so it's clear what's going on here.

I second this request. It's a bit difficult for me to understand the changes given my lack of knowledge of how the stable/internal MIR APIs compare.

[celinval]

I wonder if we could add links to the stable MIR project or its APIs so it's clear what's going on here.

I second this request. It's a bit difficult for me to understand the changes given my lack of knowledge of how the stable/internal MIR APIs compare.

Sure. Right now stable_mir and rustc_smir are new crates in the rust compiler itself. So there's nothing new, and you can apply the same logic as you currently use to check APIs from rustc_span and rustc_middle.

I will add more information to the code and to main.rs, since this code will start showing up in different parts of our compiler.

[celinval]

@zhassan-aws and @adpaco-aws, I added some documentation to our wiki instead. I hope that's what you were looking for. Cheers!