This provides most of the implementation, but there are some
things we cannot enable until we improve of kernel submit
interface, namely:

We don't expose capacity to export SYNC_FD, although we do
have the implementation in place. This requires that we
improve our kernel interface and event wait implementation
first so we can cover the corner case where the application
submits a command buffer that includes a VkCmdWaitForEvents
and tries to export a SYNC_FD from its signal semaphores or
fence before it the event is signaled and the command buffer
is sent to the kernel for execution in full.

Likewise, we can't currently import semaphores. This is because
our current kernel submit interface can only take one syncobj.
We have been working around this so far by waiting on the last
syncobj produced from the device whenever we had to wait on any
semaphores (which is obviously suboptimal already), but this
won't work as soon as we allow importing external semaphores,
as those could (and would typically) be produced from a
different device.

Once we address the kernel bits, we should come back and enable
SYNC_FD exports as well as semaphore imports.

Relevant CTS tests:
dEQP-VK.api.external.fence.*
dEQP-VK.api.external.semaphore.*
dEQP-VK.synchronization.cross_instance.*

Reviewed-by: Alejandro Piñeiro <apinheiro@igalia.com>
Part-of: <!11105>