Present extension based scheduler doesn't work well on NVIDIA drivers.
GLX_SGI_video_sync is less accurate, but is rumoured to work. See
[kwin's usage](https://invent.kde.org/plasma/kwin/-/blob/master/src/
backends/x11/standalone/x11_standalone_sgivideosyncvsyncmonitor.cpp)
Signed-off-by: Yuxuan Shui <yshuiv7@gmail.com>
Factored out vblank event generation, add abstraction over how vblank
events are generated. The goal is so we can request vblank events in
different ways based on the driver we are running on.
Tried to simplify the frame scheduling logic, we will see if I succeeded
or not.
Also, the logic to exclude vblank events for vblank interval estimation
when the screen off is dropped. It's too hard to get right, we need to
find something robust.
Signed-off-by: Yuxuan Shui <yshuiv7@gmail.com>
