MediaMuxer: add wrapper for MediaMuxer constructor

Added MediaMuxer::create(), that validates the input arguments.
All the calls to MediaMuxer's default constructor are now replaced
by MediaMuxer::create().

MediaMuxer's default constructor is still retained as public for the
time being and will be made private in a subsequent CL.

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

Change-Id: I166caa65708cd1ba2076bbbda4c425f534ba2887