Add ambient backlight event type

Add ambient backlight event type in media quality manager for CTS.

Test: atest CtsMediaQualityTestCases:android.media.mediaquality.cts.MediaQualityTest
Flag: android.media.tv.flags.media_quality_fw
Bug: 377079429
Bug: 388925595

Change-Id: I14778d826dd8f82a8c26adefbd300d734fac0ab0