[power-throttling] Fine tune algorithm

This change fine-tunes the power-based throttling algorithm to
take into account the current brightness instead of max brightness for the
Throttling limit.
It also fixes underutilzation of power and resets the pmic handler,
if thermal state is 0.

Test: Manual and updated atests
       atest DisplayServiceTests
       atest com.android.server.display.brightness.clamper.BrightnessPowerClamperTest
Flag: com.android.server.display.feature.flags.enable_power_throttling_clamper
Bug: 302814899
Change-Id: I754c86c26d51fde1ccd6c91ba649f58fc73afcd2