This reverts commit 97b526c192.
It broke the API, and assumed no other APIs used multiple semaphores.
This also disallowed certain optimizations to happen.
Dealing with APIs that give or expect single semaphores is easier when
we use per-image semaphores.
The idea was to allow separate planes to be filtered independently, however,
in hindsight, literaly nothing uses separate per-plane semaphores and it
would only work when each plane is backed by separate device memory.
This commit adds a Vulkan filtering infrastructure for libavfilter.
It attempts to abstract as much as possible of the Vulkan API from filters.
The way the hwcontext and the framework are designed permits for parallel,
non-CPU-blocking filtering throughout, with the exception of up/downloading
and mapping.
Lynne