stagefright: MediaCodec::releaseAsync()

releaseAsync() kicks off shutdown sequence but don't wait for it to
finish. Instead, mark itself as pending removal to the resource manager.

Bug: 129008570
Test: atest CtsMediaTestCases -- --module-arg CtsMediaTestCases:size:small
Test: ResourceManagerServce_test
Change-Id: I119945684e4c101c44d64c13913fa01320662fa9