Describe the pull request

This PR allows command queues to take temporary shared ownership over one or more command buffers during submit. Ownership is held until the submitted fence value has been surpassed. It is released during waitFor. This allows for temporary command buffers to stay alive, until they are executed. It is no longer necessary to manually manage and release such command buffers.

Similarly, transfer operations inside command buffers can take a temporary shared ownership over resources. If a command queue waits for a fence, all completed command buffers are asked to release the references shared this way. This is useful to implement "fire-and-forget" buffers, for example for staging purposes.

To make this possible, all command buffers are stored in shared pointers by default and the command queue only accepts shared command buffer pointers on submission. For resources, shared ownership can be enabled using asShared.