Show button to open knetattach inline with URL nav on remove:// view

This is a backport of b1cadeba

  From b1cadeba Mon Sep 17 00:00:00 2001
  From: Nate Graham <nate@kde.org>
  Date: Tue, 15 Dec 2020 23:03:00 -0700
  Subject: [PATCH] Show button to open knetattach inline with URL nav on
   Remote:// view

  In conjunction with
  frameworks/kio!260,
  the net result is to hide the knetattach launcher in the view, and show
  it inline with Dolphin's URL navigator toolbar when viewing the
  remote:// view, just like how we add an "Empty Trash" button when
  viewing trash://.

The backport ensures that even with frameworks << 5.78 only one network
button is shown.

BUG: 431626