Use DocumentFile and DocumentsContract to support more operations
on content URIs, such as:
* listing files and subdirectories with usable content uris
* mkdir, rmdir
* creating non-existing files under a tree uri
* remove
And since dealing with content URIs require some level of user
interation, manual tests were added to cover what's been implemented.
Note: parts of the code were from from BogDan Vatra <bogdan@kdab.com>.
Pick-to: 6.4 6.2
Task-number: QTBUG-98974
Task-number: QTBUG-104776
Change-Id: I3d64958ef26d0155210905b65daae2efa3db31c1
Reviewed-by: Ville Voutilainen <ville.voutilainen@qt.io>
