Better caching and updating for dynamic list provider

This updates the way the items of the new dynamic directory provider are getting updated.

- Do not reset and refresh on window close/open all the time
- Update only on database changes

Some exceptions where no update takes place:
  - Library is currently updating
  - No corresponding items to the library update (e.g. video library update and only audio items in the list)
  - Window of the container is not active (update on next activation)
  - A plugin provides the content, it can handle updates itself