Add standalone ART gtests to `TEST_MAPPING` group `mainline-presubmit`.

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

  $ art/test/utils/regen-test-files
  Generated Blueprint files for 626 ART run-tests out of 930 (67%).
  Generated TEST_MAPPING entries for 376 ART run-tests out of 930 (40%):
    376 ART run-tests (100%) in `mainline-presubmit` test group.
     19 ART gtests (100%) in `mainline-presubmit` test group.
    376 ART run-tests (100%) in `presubmit` test group.
     19 ART gtests (100%) in `presubmit` test group.
      0 ART run-tests (0%) in `postsubmit` test group.

Test: Rely on TreeHugger presubmits
Bug: 178703264
Bug: 152379281
Change-Id: I84da85e33c7ac1e44361bbb0b3bfa399ceab9b2f
2 files changed