vrend,caps: Add a caps feature check version

When we add new feature checks on the host side that is used to enable a cap conditionally in the guest that was enabled unconditionally before we might end up with a feature regression when a new mesa version is used with an old virglrenderer version that doesn't check for that cap.

To work around this problem add a version id to the caps that corresponds to the features that are actually checked on the host so that it can be checked in the guest whether this cap was actually checked for or whether it should be enabled unconditionally.

The id should be incremented whenever a new feature check is added that might result in a feature regression in the guest when run on an old host.

The mesa side is here: mesa/mesa!534 (merged)