Fix MediaPlayer construction with AUDIO_SESSION_ALLOCATE.

The cl modifies the native initizalization code, so it's possible
to pass explicit session id during construction of native MediaPlayer
instance (prior to this change, the native constructor would always
allocate new session id from audio server, even though in some cases it
might have been immediately changed to exliplicitly requested session id).

Bug: 263373078
Bug: 263362598
Test: atest MediaPlayerUnitTest
Test: atest CtsMediaAudioTestCases CtsMediaPlayerTestCases

Change-Id: Id3b52d6432a929ce5ce09f76fb7640857667358b