dzn: Use the vk_sync/vk_queue infrastructure
This is an attempt at re-using the vk_sync/vk_queue infrastructure to replace our Fence/Semaphore implementation by the standard one and get allow us to use a bunch of common functions.
Completely got rid of the export/import logic that was present in v1, which makes things a lot simpler.
(based on !54 (merged))
/cc @jenatali @jekstrand.
Edited by Boris Brezillon