vulkan: async and event fixes (#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
