chore(ci): rename 'new tests' jobs to 'new and changed tests' (#89054)
## Summary
Renames the CI job display names from 'Test new tests' to 'Test new and
changed tests' to accurately reflect what these jobs do.
The `get-changed-tests.mjs` script uses `git diff --name-only` which
detects both added and modified files, so the job names should reflect
that they test both new AND changed test files.