MediaMuxer: throw exception if create() fails for muxer

This patch also updates the documentation for MediaMuxer()

Bug: 146417874
Test: atest CtsMediaV2TestCases:MuxerTest
Test: atest CtsMediaV2TestCases:MuxerUnitTest
Test: CtsMediaMuxerTestCases

Change-Id: Ia07a7e6864d6c27476b960069a6f4e8ac0de8255
2 files changed