Create ActivityDisplay if its registered in DisplayManager

Activity manager is notified asynchronously when new display is
created. Because of that someone may try to access or use it
before AM is aware of it, e.g. launch an activity to a just
create virtual display.
This CL guards the cases where we try to use a display by id in
AM and creates a new instance if needed.

Bug: 34262188
Test: android.server.cts.ActivityManagerDisplayTests
Test: #testImmediateLaunchOnNewDisplay
Test: go/wm-smoke
Change-Id: Iab0871708145aa80ff252a0c764beb6a3b5dc42d