AOD: Keep brightness sensor registered while covered

Keeps the brightness sensor registered even if proximity is near.

This allows the brightness sensor to react faster after coming out
of a pocket.

Also wait with unpausing AOD until the brightness sensor reports
a valid brightness again.

Bug: 65010918
Test: Cover prox sensor for 10s, verify with 'adb shell dumpsys sensorservice' that the binned brightness sensor is still registered.
Test: runtest -x packages/SystemUI/tests/src/com/android/systemui/doze/DozeScreenBrightnessTest.java
Test: runtest -x packages/SystemUI/tests/src/com/android/systemui/doze/DozeTriggersTest.java
Change-Id: Ife1bb7399a7ad8a15b1f4d210bb38044cbe9d3ae