Split RefreshRateConfigsTest#groupSwitching

The groupSwitching test contains several sub tests which are
hard to follow beacuse each following test overrides some of
the previous preconditions. This CL splits the test into
multiple subtests with clear preconditions.

Test: atest RefreshRateConfigsTest
Bug: 183128900
Change-Id: I2898d7bff42b22d58b39d5b4a500ceb02e339573