Prevent adding methods in WindowInsetsAnimationController

It is a public interface which should not have different versions
sharing the same API level. This CL moves the methods to an
@hide interface.

Fix: 198614722
Test: atest android.signature.cts.api.current.SignatureTest
Change-Id: Ib02708aeb1ec960bda20b6b60d4df6f0c9b4d9d6