SDK / exoplayer

This removes the prior restriction of needing to remember not to crop and set aspect ratio in the same Presentation.Builder, and makes each class a bit more targeted.

This is partially made feasible by the past work to merge consecutive
MatrixTransformations into a single MatrixTransformationFrameProcessor, which
ensures that there's no loss in quality between successive MatrixTransformations.

PiperOrigin-RevId: 453660582