Max animation time for idle screen brightness mode

- Switch animation time cap when switching between idle and interactive
  screen brightness mode.
- Fallback to interactive mode value if no value is specified
- Gate this behind flag

Additionally:
- add tests in DisplayDeviceConfigTest for fallback values for auto brightness light debounce

Bug: 252770716
Test: atest DisplayServiceTests
Test: adb shell setprop persist.sys.com.android.server.display.feature.flags.enable_adaptive_tone_improvements_1 1

Change-Id: Iee8d299f4ae9c2ed9e1b96e539480eebe4a986f7