fix: update coverage.include and coverage.exclude

[DevJoaoLopes]

Description

Fixes coverage.include/coverage.exclude glob matching so it behaves like test.include/test.exclude (relative to the project root), addressing Vitest v4 regressions reported in #9395.

In v4, matching was done against the full (absolute) filename with picomatch using contains: true and ignore, which made patterns such as ./*.ts or **/foo/** unexpectedly match parts of the absolute path (including the CWD), causing everything to be excluded.

This change:

• Matches include/exclude against the path relative to each project root when the file is inside the project, so top-level-only excludes like ./*.ts work as expected.
• Avoids excluding the whole project when the CWD contains an excluded segment (e.g. /.../foo/...), by using relative paths for in-project files and only using the absolute filename for truly external files.
• Keeps allowExternal: false semantics by skipping external files instead of incorrectly failing matches for everything.
• Adjusts the glob cache key to include the root (so multi-project roots don’t share incorrect cached results).

fix #9395

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[AriPerkkio]

Could you check the failing tests and add new tests to test/coverage-test to validate this fix? Or maybe use the test/coverage-test/test/include-exclude.test.ts.

[DevJoaoLopes]

Could you check the failing tests and add new tests to test/coverage-test to validate this fix? Or maybe use the test/coverage-test/test/include-exclude.test.ts.

@AriPerkkio Sure, I apologize for not doing it from the beginning... I'll work on it. 😅