chore: Fix test coverage issues

[just-boris]

Description

Fix coverage issues

1. Switch to v8 provider because it provides more accurate numbers
2. Rename vite.*config.mjs files to vite.config.*.mjs to follow the standard naming convention: https://github.com/vitest-dev/vitest/blob/fee7d8be9d6e6f710270600ae91fa35d861b7075/packages/vitest/src/defaults.ts#L6

Related links, issue #, if available: n/a

How has this been tested?

See PR build report, the coverage is finally above 90%

Review checklist

The following items are to be evaluated by the author(s) and the reviewer(s).

Correctness

• Changes include appropriate documentation updates.
• Changes are backward-compatible if not indicated, see CONTRIBUTING.md.
• Changes do not include unsupported browser features, see CONTRIBUTING.md.
• Changes were manually tested for accessibility, see accessibility guidelines.

Security

• If the code handles URLs: all URLs are validated through the checkSafeUrl function.

Testing

• Changes are covered with new/existing unit tests?
• Changes are covered with new/existing integration tests?

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 91.18%. Comparing base (fd52d40) to head (5816a22).

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #297      +/-   ##
==========================================
+ Coverage   83.19%   91.18%   +7.99%     
==========================================
  Files          60       62       +2     
  Lines        1666     4310    +2644     
  Branches      446      728     +282     
==========================================
+ Hits         1386     3930    +2544     
- Misses        280      377      +97     
- Partials        0        3       +3     

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[michaeldowseza]

Switch to v8 provider because it provides more accurate numbers

Is it something we should consider for our other packages that currently use istanbul?

[just-boris]

Yes, for all vitest based projects v8 is preferred.