add classes to help RRO theme test

The final UI result is impacted by DocumentsUI, providers, and RRO
overlay package. To verify the UI component is very important.
Especially, it needs auto-testing.

ScreenshotCaptureRule will capture screen when the test fail.

FuzzyColor is help to get the color histogram with fuzzy method.

Test: atest com.android.documentsui.picker.PickActivityTest
Bug: 125124718

Change-Id: Ifdbee5009323df4203140a6d03179b5ab38aabfc