fdo#79011: Properly implement the search results dialog as modeless.

It's unfortunate that adding a modeless dialog is such a pain.  But we
still need to implemenet this properly else we'll leak at best, or end
up with tons of weird bugs at worst.

(cherry picked from commit 81c492ef18b04cc283561018d69818cbca7f83ef)

Conflicts:
	sc/inc/sc.hrc
	sc/sdi/cellsh.sdi
	sc/sdi/scalc.sdi
	sc/source/ui/view/cellsh1.cxx
	sc/source/ui/view/tabvwsh.cxx

Change-Id: Ie03260f288fad76f994d0ca6a8b1feeade299ffd
Reviewed-on: https://gerrit.libreoffice.org/9451
Reviewed-by: Eike Rathke <erack@redhat.com>
Tested-by: Eike Rathke <erack@redhat.com>