feat(stdlib)!: update stdlib functions to return bool where appropriate

[TomAFrench]

Description

Problem*

Resolves

Summary*

This PR sets out to enforce proper types on several stdlib functions which return Field to represent a boolean value. I assume this was done before we had a proper boolean type but it should now be updated.

This isn't time sensitive so we can merge this whenever we feel it's appropriate to make a breaking change to the stdlib.

Documentation

• This PR requires documentation updates when merged.

  • I will submit a noir-lang/docs PR.
  • I will request for and support Dev Rel's help in documenting this PR.

The function signatures for several stdlib functions has changed and so code examples must be updated.

Additional Context

PR Checklist*

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

[TomAFrench]

We could also take this opportunity to remove merkle::check_membership as it's pretty redundant with merkle::compute_merkle_root.

[kevaundray]

One thing on my mind with this PR is; who is applying the relevant constraints.

ie does Noir constrain it to be a boolean or does the backend calling it constrain it to be a boolean based on the function being called. In our case right now the backends is implicitly doing it, but perhaps we need to put this information somewhere so that folks don't need to dig into the codebase.

(This is not blocking for this PR)

[jfecher]

👍

[kevaundray]

We could also take this opportunity to remove merkle::check_membership as it's pretty redundant with merkle::compute_merkle_root.

Gonna merge this, lets open up a new PR for that ser :)