Tag brightness APIs with @SystemAPI

Make the API for tracking brightness
slider events and setting brightness
curves @SystemAPI and @TestAPI
Add developement scope to the brightness
slider events permission to allow cts
testing.

Bug: 69405990
Test: atest android.permission2.cts.PermissionPolicyTest#testPlatformPermissionPolicyUnaltered
Test: atest BrightnessTrackerTest
Change-Id: I39b0b26454528425b62cf99dc8bbccded4e14a18