Prepare comments and annotations for OverlayManager public API

This patch adds the following items.
* OverlayManager class comments.
* Move the class comments related to OverlayManagerService to @hide
  constructor
* Replace @link with @code in comments because of linking to @hide API
* add @SuppressLint("ReferencesHidden") for APIs will be public API
* Add @see for 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 \
        idmap2_tests
Change-Id: I0ea9a73e61ac4e435f1ebbaa5bd65bdfe4bc9d25