Add functional tests for desktop mode scenario tests.

These will be used for setting up post-submit tests. As this is a
lightweight module, it will eventually be scheduled to run as part of
presubmit for WindowManager CLs

Test: scheduled test run on ABTD using gcl config
Bug: 356835482
Flag: NONE added new tests

Change-Id: I2f8d4846bd3f34a9db5be4f5909944190782f244