xwayland dri3: Implement XCB_PRESENT_OPTION_ASYNC_MAY_TEAR
What does this MR do and why?
This MR allows Xwayland OpenGL/OpenGL ES apps to control tearing on Wayland (using the in-game or app option to enable/disable Vsync). Or user can enable tearing (disable Vsync) using environment variable
vblank_mode=0
.