lavapipe: enable vulkan 1.2 support.

The remaining extensions are optional features, just turn on vk 1.2
with them reporting as off.

Reviewed-by: Roland Scheidegger <sroland@vmware.com>
Acked-by: Mike Blumenkrantz <michael.blumenkrantz@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/12953>