Fix coverage check

[wulfraem]

Description of change

This PR updates the code instrument-coverage flag to be set as a stable option, as this option has moved from unstable to stable.

Updated clippy found unexpected cfgs has_i128 and has_u128. As those are set in the build.rs, linting rule has been configured in Cargo.toml to allow the known two cfgs.

It also adds a changelog entry for the previous (#223).

Type of change

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• Bug fix (a non-breaking change which fixes an issue)
• Enhancement (a non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation Fix
• Chore

How the change has been tested

Code coverage command from CI ran successfully in local tests.

Change checklist

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• I have followed the contribution guidelines for this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes