feat(frontend): Where clause on impl

[vezenovm]

Description

Problem*

Resolves #4508

Summary*

This enables the simple functionality of being able to declare a where clause directly on a struct implementation such as below:

impl<T> MyStruct<T> where T: MyEq {
    fn my_eq(self, other: Self) -> bool {
        (self.a == other.a) & self.b.my_eq(other.b)
    }
}

The code above is essentially syntactic sugar where we every method in the struct impl has a where clause. As the logic for resolving trait constraints already exists this PR really just updates the parser to accept where clauses and during definition collection attaches them to each method in an impl.

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.

[github-actions]

🚀 Deployed on https://6679df5139fd8c382cfa4791--noir-docs.netlify.app

[vezenovm]

Converting back to draft because the formatter needs updating

[vezenovm]

Converting back to draft because the formatter needs updating

The formatter was deleting the where clause on impls. I did a quick hack to get things working. I could make it more robust but I feel it can also be done in a follow-up to improve the robustness of formatting impls in general.

We should also maybe consider committing some time to larger formatter refactors/testing again.

[jfecher]

LGTM

Looks like you'll need to revert my "remove the mut" suggestion, my bad

[github-actions]

FYI @noir-lang/developerrelations on Noir doc changes.