vulkan: async and event fixes (llama/20518)

vulkan: async and event fixes (llama/20518)

* vulkan: fix event wait submission, event command buffer reset

* fix event command buffer reset validation error

* also reset command buffers before reuse

* use timeline semaphores instead of fences for event_synchronize

* don't use initializer list for semaphore wait info

* use multiple events to avoid reset issues

* fix event reuse issue with multiple vectors

* add semaphore wait condition also if compute_ctx already exists

* remove event pending stage