Emit unreachable arm warning for OR match arms

[ironcev]

Description

This PR fixes #6388. If a whole OR match arm is unreachable a warning will be emitted like in this case:

match v {
    1 => (),
    2 => (),
    1 | 2 => (), <<<--- Warning emitted here.
    _ => (),
};

The PR strictly fixes the issue reported in #6388. It does not fix a previously known, more general issue, described in #5097 where we expect warnings to be emitted also on individual elements of an OR arm, even if the whole arm is reachable. E.g.:

match v {
    1 => (),
    2 => (),
    1 | 3 => (), <<<--- Warning should be emitted here that `1` is not reachable.
    2 | 4 => (), <<<--- Warning should be emitted here that `2` is not reachable.
    _ => (),
};

Fixing this issue requires more invasive restructuring of the propagation of the collected witness information and will be done in a separate PR.

Closes #6388.

Checklist

• [x] I have linked to any relevant issues.
• [x] I have commented my code, particularly in hard-to-understand areas.
• [ ] I have updated the documentation where relevant (API docs, the reference, and the Sway book).
  • [ ] If my change requires substantial documentation changes, I have requested support from the DevRel team
• [x] I have added tests that prove my fix is effective or that my feature works.
• [ ] I have added (or requested a maintainer to add) the necessary Breaking* or New Feature labels where relevant.
• [x] I have done my best to ensure that my PR adheres to the Fuel Labs Code Review Standards.
• [x] I have requested a review from the relevant team or maintainers.

[codspeed-hq[bot]]

CodSpeed Performance Report

Merging #6505 will not alter performance

_{Comparing ironcev/6388-no-warning-for-overlaps-in-pattern-matching (7ed5f86) with master (eaac649)}

Summary

✅ 21 untouched benchmarks