Prepare comments and annotations for OverlayManagerTransaction public API

This patch doesn't change any logic or data type. It does the
followings.
* Add class comments for self-targeting
* Add comments and annotations for the APIs will be public
* Add @hide for the APIs not to public
* Add ctor OverlayManagerTransaction(OverlayManager) for apps
* Separate the comments for OverlayManagerService to private
  constructor
* @SuppressLint("NullableCollection") because it's null when the
  request type is only unregisteration.
* Make classes declaration to be final because of Parcelable.
* Refactor two functions from OverlayManagerTransaction.Builder
  * registerFabricatedOverlay
  * unregisterFabricatedOverlay
* Add @see relevant APIs.

Bug: 205919743

Test: make update-api ; make
Test: make online-sdk-docs offline-sdk-docs
Test: atest \
        OverlayHostTests \
        OverlayDeviceTests \
        SelfTargetingOverlayDeviceTests \
        OverlayRemountedTest \
        FrameworksServicesTests:com.android.server.om \
        CtsContentTestCases:android.content.om.cts \
        CtsContentTestCases:android.content.res.loader.cts \
        idmap2_tests
Change-Id: I4588d2399d5084abf067dc9ac40e22ccd167de19