[OE_BP PR2890] changed: Make more obvious we're passing a CFileItem
[OE_BP PR2890] removed: BackGroundInfo Loader multithreading (no longer needed)
[OE_BP PR2890] changed: Split background info loading into a 2 stages

This allows us to first perform loading of cached (fast) stuff and after that load the lookup (slow) stuff (partially fixes #14071)
[OE_BP PR2890] changed: Renamed m_database to m_video/m_musicDatabase for clarity
[OE_BP PR2890] changed: Use a member variable for the texture database

This speeds up thumb loading considerably. This also gets rid of the Initialize/Deinitialize ThumbLoader functions
[OE_BP PR2890] fixed: Music thumb loading for files view was slow

This was caused by the fact that we never checked for cached images for music items
[OE_BP PR2890] fixed: Thumb/flag extractions were never stored when used outside the bg infoloader

Also factored out some (obsolote?) code as a bonus
[OE_BP PR2890] fixed: MusicInfoTag loader locked up after 9752e490e40e69d53e9dbb10a972dff533192570
[OE_BP PR2890] fixed: Little fixup for 94817e6fa85e2e0b39d1f0f96795435a4256fe7b (thanks JM)
[OE_BP PR3000] Add a mutex for the db connection. Fixes #14500
[OE_BP PR3000] protect the multithreaded use of the database from child classes.