Folder View: Create drag pixmap with device pixel ratio
Ensures the drag pixmap is crisp.
Not entirely sure how that would fare with mixed dpi or if that’s even possible.
Needs https://code.qt.io/cgit/qt/qtdeclarative.git/commit/?id=91e75fc3478f4cbef1a1e5449e8f9236af7397ab (but will no-op otherwise)