fix(tests): Prevent EOF error while running test programs

[aakoshh]

Description

Problem*

Resolves #6445

Summary*

Running test_programs locally with cargo test -q -p nargo_cli --test execute occasionally failed with EOF and other parsing errors. This was because the test_foo and test_foo_brillig tests could end up running at the same time, and when e.g. test_foo tried to read the compiled artefact JSON file, test_foo_brillig was writing to it with different parameters.

The PR adds a mutex for each test name that allows multiple variants on the same directory to coordinate.

Additional Context

This PR is an extension of #6429 which already fixes this issue, but disables the inliner aggressiveness in the matrix. This way people who often run the tests locally (e.g. @asterite working on parsing) can run the tests without false positives. Doing the same without the #[test_matrix] approach would be more difficult because there was a separate call to the test function generator for _brillig, and we need one mutex; this way it's all covered by one generator.

I tried using #[serial_test(<test_name>)] instead of a mutex but it doesn't work well with #[test_matrix].

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.

[asterite]

Looks great!