SF: Clean up DisplayModeSwitchingTest

Use the ModeSettledTo and ModeSwitchingTo helpers in all tests. Clean up
tests for brevity (e.g. minimal mock::createDisplayModeSpecs parameters)
and consistency (e.g. NO_ERROR checks).

Flag: TEST_ONLY
Bug: 241285876
Test: DisplayModeSwitchingTest
Change-Id: I5d92eae231d1b1a2c25f89ea7de4987569d9905e
2 files changed