SDK / exoplayer

This change adds ExternalTextureManager which implements
InputListener to only queue input frames to the
ExternalTextureProcessor when it is ready to accept an input
frame. This replaces the old retry-logic in GlEffectsFrameProcessor.

Before this change, the retrying in GlEffectFrameProcessor wasted
CPU time if input becomes available faster than the
ExternalTextureProcessor can process it.

PiperOrigin-RevId: 467177659
(cherry picked from commit d7bf1ed2)