Currently `FrameProcessor.releaseOutputFrame()` method supports
Release at a specific system time
Drops the frame
This API is not that convenient to use when the caller wants to release a frame, now, regardless of the release time. A use case is to release (present) a frame when no frame is shown for a while, and it's thus better to just release the frame, now.
Currently if MCVR wants a frame to be rendered now, MCVR calls release frame with a set offset like 10us: `releaseOutputFrame(System.nanoTime() + 10_000)`. The 10us offset is to prevent the frame processor dropping the frame, due to thread hopping delays.
To make the API better usable, consider adding a mode for releasing the frame now, like (bold marks the new mode)
- Use C.TIME_UNSET to drop
- **Use -1 to release the frame immediately, or**
- Use an actual release time.
PiperOrigin-RevId: 479044215
