It is now up to the user to request thumbnails generation.
It allows lazy loading, and prevents us from potentially generating
thousands of thumbnails for nothing when indexing an entire network
drive.

We don't need to know if a video track was detected or not anymore

We now fallback to starting a playback early, no need for the old
complicated and full of special case code

This seems to happen on some devices, with folders ending with a
trailing dot
Fix https://trac.videolan.org/vlc/ticket/19909

We were leaving potentially scheduled parser tasks behind

is_present doesn't exist, and we want to reset the count for all tasks
anyway. It will start or not depending on the file presence, but we
don't need to care when reseting

This version will ensure all the File have an associated Task, to avoid
some content not appearing because it wasn't analyzed

This eases up recreating a task from a file, in case we failed to do so
during the original migration

Which is more appropriate for what this function does

That makes it 2 forgotten tables...

If any, they are signaled through an sqlite exception