Parcel: flag marshall/unmarshall with ByteBuffer APIs

Put these APIs behind a flag so we could add them to the SDK,
at some point.

Remove the unit test for these APIs.
Another change is moving these tests to CTS, where they belong.

Bug: 401362825
Flag: android.os.parcel_marshall_bytebuffer
Change-Id: I2edcb2a5de7b4e07a36986b38246d4410bde2f75