fdo#86476 add icons to sheet management menu and context menu entries

Change-Id: I3d286487a8b81d440f480a528298c815f295fc92
Reviewed-on: https://gerrit.libreoffice.org/13087
Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>