It doesn't make sense to define `onTranscodingProgress` inside of `mediaProcessConfig`. Instead it makes sense to define `onTranscodingProgress` callback at callsite and pass into `mediaProcessConfig`. This also makes `mediaProcessConfig` more generally useful.
I initally adding the `onTranscodingProgress` stuff to InputStateContainer so my bad.
(I'm NOT planning on doing any more refactoring here. This was confusing and 2 min change so I just made it.)