Add ZenDeviceEffects to ZenModeDiff

Adds class to diff ZenDeviceEffects objects, and associated tests.

Unlike other objects diffed in ZenModeDiff, ZenDeviceEffects uses
private final fields and a builder, so for testing purposes we need to
modify the reflective field aggregator in the test file to consider
final fields (rather than skipping them).

Bug: 319241807
Test: atest ZenModeDiffTest
Flag: android.app.modes_ui
Change-Id: I8a59ce6711a401a87b1a1e72f7e0f05fe56a5d72