Atest: add hinter when no valid test to run.

Bug: 176822924

Test: m atest
atest-dev ChooserActivityTest#TwoVisibleImagePreview
 # see the highlighted message.
atest-dev -v ChooserActivityTest#TwoVisibleImagePreview
 # see both highlighted message and debugging info.

Change-Id: I89fb5cac0c3aead324885e4438e2cbd812637ce5
1 file changed