Move dismiss split screen tests to another package to comply with SLO

Currently WMShellFlickerTestsSplitScreenEnter takes 10min and WMShellFlickerTestsSplitScreenOther takes 26min

Bug: 288483593
Test: atest WMShellFlickerTestsSplitGroup1 WMShellFlickerTestsSplitGroup2
Change-Id: Id35ded4e40db0a2819cfd42e9cb37a0a9c4dde8a
1 file changed