Adding Brightness Percent check to ABC

If the brightness change is so low that it passes the float-equals
check, then also check against the difference in Brightness Percent.
If the change is still move than a defined percent limit,
continue with the brightness change.

Bug: 408929889
Test: atest AutomaticBrightnessControllerTest
Flag: EXEMPT bug fix
Change-Id: Iaa6f3fd5e36dc2294518acebb58b7bbddf226255