Restore former position of "Create New" menu item in viewport context menu

Summary:
I've seem various complaints from users about the fact that the {nav Create New...} menu
item in the viewport context menu is now below {nav Open With} item. All the other
changes to menus seem to have been well-received but this one has garnered criticism.
Looking through D23757 and D11884, I can't actually see that this was intentional, so
it might even be a bug.

Either way, this patch restores the old position of the {nav Create New} menu items at
the top of the Viewport context menu.

BUG: 417640
FIXED-IN: 20.04.0

Test Plan: {F8093605}

Reviewers: #vdg, #dolphin, elvisangelaccio, ndavis

Reviewed By: #vdg, ndavis

Subscribers: asturmlechner, markuss, kfm-devel

Tags: #dolphin

Differential Revision: https://phabricator.kde.org/D27267