*** Original commit ***
Rollback of https://github.com/google/ExoPlayer/commit/f13f87ab58f7ee0de7d097364343f564ec8300a7
*** Original commit ***
Create InAppMuxer in transformer
To use the InAppMuxer, the client needs to pass InAppMuxer Factory.
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PiperOrigin-RevId: 531470081
(cherry picked from commit 19bfa54011b5dd6b21c7839e1b488fc2b0904cbe)
