Support power-based throttling.

This change adds a smart throttler based on power-consumed
by the display. We use the power IC HAL apis to provide the
power consumed, and throttle brightness in order for display to stay
within budget for power-consumption.

This feature is feature-flag protected.

Bug: 261221454
Bug: 294777007

Test: multiple tests were added. Also manually tested.
Change-Id: Ia7d3e54073b0855200818a47d0029d715cd1b27e