SDK / exoplayer

TransformationException error codes were previously tied to OpenGL
but other FrameProcessor implementations are possible. So this CL
renames the error codes.
Also, remove GL_INIT_FAILED error code, as FrameProcessor
implemenations may initialize resources on a background thread
after the factory method returns, so it's not obvious how to
distinguish between initialization failures and processing failures.

PiperOrigin-RevId: 463704902
(cherry picked from commit bac323d3)