[CONTENT] Support for music track looping

[src52]

Content/Plugin Description

Players should be able to enable the Loop button in the music tab to have music tracks repeat after they finish playing.

Acceptance Criteria

• [ ] Enabling the loop button should make the currently selected music track repeat.
• [ ] Disabling the loop button should make the music stop once it's done playing.
• [X] The loop button state should be saved and loaded from the character file.

Additional Information

This feature seems like it was meant to be implemented on the client-side. If so, once we're able to de-obfuscate the client more, we should consider removing the server-side implementation in favor of a client-sided one.