Made favorites dragable

fixes #26624 (closed), fixes #32892 (closed) There were other instances of this issue but i was unable to find more on github. Basicly everytime you could drag a regular file you were unable drag a favorite.

Changes:

• a selection of favorites is now of type "files" or "files_and_dirs" like any other file/dir selection
• information regarding favorites is now stored under "favorite"
• selections from both favorites and non-favorites can be dragged and used
• the file dock still won't accept a mixed selection of favorites and non-favorites. This avoids confusion when moving or reorganizing files and is in line with current behavior.

What should break:

• Nothing. filesystem_dock.cpp is the only place even aware of favorites existing. The other code expects just regular files and should now work.

Todo:

• it is possible to select the same file twice as favorite and non-favorite