This commit scraps a bool to signal to recreate the session parameters,
but instead destroys them, forcing them to be recreated.
As this can happen between start_frame and end_frame, do this
at both places.
Move the slice offsets buffer to the thread decode context.
It isn't part of the resources for frame decoding, the driver
has to process and finish with it at submission time.
That way, it doesn't need to be alloc'd + freed on every frame.
