2/ Fix flaky in WMShellFlickerTest legacySplitScreen tests

b/177374067 indicate OpenAppToLegacySplitScreenTest still flaky
1) Extend the filter in visibleLayersShownMoreThanOneConsecutiveEntry()
   - Toast window
2) When going split transition, waitForAppTransitionIdle() at end
3) Enable navBarLayerIsAlwaysVisible() & statusBarLayerIsAlwaysVisible()

Test: atest com.android.wm.shell.flicker.legacysplitscreen
Test: Set TEST_REPETITIONS to 100 and run flicker test stressfully
Bug: 177374067
Bug: 176923301
Bug: 176134495
Change-Id: I1caface176f4af591d5383877c81b786eb23ba58