Create new test group to split the tests

Flicker tests are taking longer than the 30min Treehugger SLO. Introduce a new test group (group 4) to reduce the flicker impact on presubmit

Bug: 197230743
Test: atest FlickerTests
Change-Id: I3373622f6fde82307b25cbab8621c1045242837d
13 files changed