Wait for transitions after connecting a display

This CL adds some explicit awaits after connecting an external display.
Currently, there is a similar wait in cuj1p/e but it seems to be better
to apply it to all scenarios.

Flag: EXEMPT - test stabilization
Bug: 442453305
Bug: 442453913
Bug: 442454448
Bug: 441594940
Bug: 442453123
Bug: 442453799
Test: atest WMShellSmokeTestsDesktopMode
Change-Id: I7e7dc3b2f05bd8bf9b87fb7c5d6f997a0a6be4cb