VSFilter: Add a new config page for the new subtitle queue options.

Also increase the max number of buffered subpic to 120.
Ensure all subtitle providers are freed when closing.

Some memory was only freed when opening a new file or closing MPC-HC.
Subtitle queue: Re-enable the queue for madVR but always advise blocking.

madVR fetches the subpic when rendering not when presenting so we can always be blocking without impacting the performance too much.