kms/impl-device/atomic: Implement mouse cursor hotspots

DRM's kms atomic code was updated to include an API to set the mouse cursor hotspot. This has historically been missing in the atomic kms which meant that the virtualized drivers which require mouse cursor hotspot info to properly render had to be put on a deny list and had to fallback to the legacy DRM kms code.

Implement the new hotspot API by checking whether the device supports hotspot properties and if it does set them on the cursor plane. This enables atomic kms on all virtualized drivers for kernels where mouse cursor hotspots are in drm core.

Related kernel patch: https://www.mail-archive.com/dri-devel@lists.freedesktop.org/msg454314.html