Put 25% of ART run-tests in `TEST_MAPPING` group `mainline-presubmit`.

Include more ART run-tests into the `mainline-presubmit` test
group. This progressive rollout is to make sure introducing ART
run-tests to this test group won't disturb/break Android presubmits.

Output of `art/test/utils/regen-test-files`:

  $ art/test/utils/regen-test-files
  Generated Blueprint files for 621 ART run-tests out of 920 (67%).
  Generated TEST_MAPPING entries for 377 ART run-tests out of 920 (40%):
    94 tests (25%) in `mainline-presubmit` test group.
    377 tests (100%) in `presubmit` test group.
    0 tests (0%) in `postsubmit` test group.

Test: Rely on TreeHugger presubmits
Bug: 178703264
Bug: 152374989
Change-Id: Idf96255ff0d591ec2d2aab63c5c6521ce26577f7
2 files changed