Add self-targeting constructor in FabaricatedOverlay

When the app wants to overlay its resource in runtime, it’s a
SelfTargeting scenario. This patch adds a new builder
constructor in FabaricatedOverlay for SelfTargeting.  It's
 `Builder(@NonNull String overlayName, @NonNull String targetPackage)`.

The app needs to pass 2  parameters.
* the overlay name
* target package to be overlaid

This patch also marks the nullability and checks the arguments of
`setResourceValue` and it needs related CTS tests to verify the
nullability.
* setResourceValue

Test: atest \
          OverlayHostTests \
          OverlayDeviceTests \
          SelfTargetingOverlayDeviceTests \
          OverlayRemountedTest \
          FrameworksServicesTests:com.android.server.om \
          CtsContentTestCases:android.content.om.cts \
          idmap2_tests

Bug: 205919743
Change-Id: Ie8e2de13076c9d28bbcf7ee52deab91114f7ec57