Draft: backport linux-drm-syncobj-v1 support

linux-drm-syncobj-v1 allows drivers and apps to synchronize KWin's buffer access to their rendering, and synchronize their rendering to KWin's buffer release. This fixes severe glitches with the proprietary NVidia driver and allows for some performance improvements with Mesa too.

I made this backport because there's serious issues with the NVidia driver, which are resolved with this + a new Xwayland release + the next NVidia driver (which will both come out a while before Plasma 6.1). It's still draft because I want some feedback and still need to do proper testing with this