Fixes https://github.com/flutter/flutter/issues/133198. Major changes: - `CommandPoolVK` is now created indirectly through `CommandPoolRecyclerVK`. - Via destructor, `CommandPoolVK` resets on a background thread via `ResourceManager`. - Removed all of the code trying to reuse/reset individual command buffers (no longer needed). - After every frame, the current/active command pool is recycled. --- _Tests secured._