Add a setting page for Reduce Bright Colors under A11y

This is essentially a copy page of ToggleDaltonizerPreferenceFragment.
We extend ToggleFeaturePreferenceFragment to maintain consistency with
other shortcut assignable a11y feature.

UI is a draft

This CL:
1) allows users to enabled/disable RBC with the a11y shortcut (button,
gestures, volume keys), if assigned
2) adds a slider and persist switch to the template
ToggleFeaturePreferenceFragment page (which already contains a feature
switch, shortcut preference, and footer description)
3) enables/disables the intensity slider when RBC is on/off
4) sets placeholders for calling into ColorDisplayService in
controllers and tests
5) follows convention set by other color transformations settings and
places feature under Experimental section in A11y settings page if
transformations can't be efficiently performed by hardware

Test: A11y setting and page appears, tested activation with shortcut,
preference controller tests
Bug: b/128465252

Change-Id: I291bb86ce3d855ce052ca70dc7a941a888e2c723