test_runner: match coverage globs against cwd-relative paths

[ace-tk]

Summary

• apply coverage include/exclude glob matching using cwd-relative paths only
• avoid accidentally excluding files when absolute parent directories contain names like test
• add a regression test for default coverage exclusion with cwd containing a test directory segment

Test plan

• not run in this environment (no local Node core build)
• run: python3 tools/test.py test/parallel/test-runner-coverage-default-exclusion.mjs

Closes: #58654

[nodejs-github-bot]

Review requested:

• @nodejs/test_runner

[avivkeller]

Ref on why this approach was chosen originally (by me): #53553 (comment)

[ace-tk]

@avivkeller

My goal was to prevent unexpected exclusions caused by absolute parent paths containing test. If changing this behavior is not preferred, I can close this and submit a docs-only clarification PR instead. Happy to follow your preferred direction.

[avivkeller]

cc @nodejs/test_runner

[ace-tk]

@avivkeller Thanks for the context and for cc-ing @nodejs/test_runner.

My intent was to avoid surprising exclusions when absolute parent paths contain test, but I understand this may conflict with the original design tradeoff in #53553