move middle::check_match and middle::const_eval to their own crate

[oli-obk]

r? @arielb1

this is groundwork for replacing const eval (running on HIR) by a constant propagator (running on MIR)

[rust-highfive]

Thanks for the pull request, and welcome! The Rust team is excited to review your changes, and you should hear from @arielb1 (or someone else) soon.

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[arielb1]

@bors r+

[bors]

📌 Commit 6f4dc87 has been approved by arielb1

[bors]

🔒 Merge conflict

[bors]

☔ The latest upstream changes (presumably #31298) made this pull request unmergeable. Please resolve the merge conflicts.

[oli-obk]

was just a change in error codes right next to one of the moved error codes

[oli-obk]

let's delay this until after typestrong const ints