Vulkan: Replace explicit command buffer submits with wrapper function

Should we ever introduce anything else that has to be done when a command
buffer is executed (e.g. invalidating constants from previous commit), we
don't have to update all the callers.

Source/Core/VideoBackends/Vulkan/Renderer.cpp

@@ -326,6 +326,7 @@ void Renderer::BeginFrame()
   // Ensure that the state tracker rebinds everything, and allocates a new set
   // of descriptors out of the next pool.
   StateTracker::GetInstance()->InvalidateDescriptorSets();
+  StateTracker::GetInstance()->InvalidateConstants();
   StateTracker::GetInstance()->SetPendingRebind();
 }