SDK / exoplayer

*** Original commit ***

Rollback of https://github.com/androidx/media/commit/07302a23bd5894d57514c68b2db499ac46726e77

*** Original commit ***

Remove `@Nullable` from `MediaSource.Factory` setters

The null-behaviour of these methods creates a minimization footgun,
because **any** call to these setters will prevent R8 from removing
the default implementation (even if it's never used by the app) - this
is because R8 can't tell the default imple...

***

PiperOrigin-RevId: 450453325