De-Mock PhysicalDisplaySwitch transit tests

These tests had everything mocked out so they weren't
really testing anything besides some very specific
implementation details. This meant that any changes
to implementation required changes to the test and the
mocks. Also, if the mocked-out impl didn't do what was
expected, the tests wouldn't catch it.

This CL changes these tests to use WindowTestsBase so
that it can run against "real" code. Then this converts
mock-impl verifications to assertions on the *effects* of
calling the tested APIs.

Bug: 325114242
Test: atest PhysicalDisplaySwitchTransitionLauncherTest
Change-Id: I656cc8a1cfb836e1c0625519ff721a84c3c0d0cb