suite/test/test_run.py: Add tests for SHA1 handling with --newest

suite/test/test_run.py: Add tests for SHA1 handling with --newest

Added two test cases to verify SHA1 handling when using --newest backtracking:

1. test_newest_success_same_branch_same_repo: Tests when ceph_branch and
   suite_branch are the same. Verifies that both ceph_hash and suite_hash
   are updated to the backtracked working SHA1.

2. test_newest_success_diff_branch_diff_repo: Tests when ceph_branch and
   suite_branch differ. Verifies that only ceph_hash is updated to the
   working SHA1, while suite_hash remains as the original suite_sha1.

Both tests verify the complete flow through collect_jobs() and
schedule_suite(), ensuring the YAML files generated for each job
contain the correct SHA1 references.

Fixes: https://tracker.ceph.com/issues/71668
Signed-off-by: Kamoltat Sirivadhna <ksirivad@redhat.com>