fix(experimental elaborator): Fix panic in the elaborator

[jfecher]

Description

Problem*

Working towards #4594

Summary*

When run on a program the elaborator would always panic previously due to FuncMetas not yet being set for other functions while one function was being elaborated. This is because we used to set them during name resolution and only check them during type checking, but now that these two passes are merged we'll need to set them all before elaboration instead.

This PR creates a new define_function_metas function to create the FuncMetas beforehand. I imagine there are more changes required here related to scoping / generics / parameters but this at least stops the panic.

Additional Context

This is the first of the elaborator PRs to feature only new changes rather than largely copied code, so feel free to critique as usual if you think a different approach would be better, notice an issue, etc.

After this PR the elaborator will run on a small example program, only producing 1052 errors in the standard library 🙂. Most of these errors appear to be variants of "no method named '...' found for ..." and "no matching impl found for ..."

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]

-            let mut program_table = table!([Fm->"Package", Fm->"Function", Fm->"Expression Width", Fm->"ACIR Opcodes"]);
+            let mut program_table =
+                table!([Fm->"Package", Fm->"Function", Fm->"Expression Width", Fm->"ACIR Opcodes"]);

^Diff from the cargo fmt test.

@TomAFrench Was the cargo fmt version on the CI updated? I don't get this locally. In fact, running cargo fmt locally will undo this change. I'm using:
cargo 1.74.1 (ecb9851af 2023-10-18) and
rustfmt 1.6.0-stable (a28077b 2023-12-04)

[TomAFrench]

We didn't have protection against pushing directly to master (I've turned it on now) and I accidentally pushed there rather than to a fresh branch for a small change which caused this issue for PRs building off of that commit. This is fixed now.

[TomAFrench]

I've merged in master so this branch has the fix.