feat: allow usage of noir #[test] syntax in stdlib

[TomAFrench]

Description

Problem*

Resolves

Summary*

Running tests within the Noir stdlib is a little complicated as nargo will not accept it as a regular crate as the stdlib uses features which are disallowed in other crates. This means that in a number of cases we're placing stdlib unit tests inside of the test_programs instead of just using the #[test] format inside of the stdlib itself.

This is suboptimal as it separates the implementation from the tests in the repository and once #4491 is merged, it will be impossible to use this method to test any private functions within the stdlib.

This PR then adds a new integration test which is equivalent to running nargo test on the stdlib and moves some tests over to the stdlib as an example.

Additional Context

Documentation*

Check one:

• No documentation needed.
• Documentation included in this PR.
• [Exceptional Case] 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.

[TomAFrench]

Ideally we'd have the rust test code closer to the stdlib but it needs access to the test runner so must be in either nargo or nargo_cli.

[vezenovm]

Looks good. You could probably also move over the bounded_vec tests under noir_test_success, but I'm not sure on the best place for those tests as it doesn't use any would-be private functions.

[TomAFrench]

Yep, I wanted to do this separately however as it's going to cause ripple effects into the docs.