PNS: Allow snap to temp hidden

The IFACE for kicad refers to the board hidden state, not the
temporarily hidden state used by the router.  We allow snapping to items
that have been removed by the temporary router state to provide snapping
to original track location.

Fixes #1827 | https://gitlab.com/kicad/code/kicad/issues/1827

(cherry picked from commit 1e64524afb)

pcbnew/router/pns_kicad_iface.cpp

@@ -1104,6 +1104,10 @@ bool PNS_KICAD_IFACE::IsItemVisible( const PNS::ITEM* aItem )
             && item->ViewGetLOD( item->GetLayer(), m_view ) < m_view->GetScale() )
         return true;
 
+    // Items hidden in the router are not hidden on the board
+    if( m_hiddenItems.find( item ) != m_hiddenItems.end() )
+        return true;
+
     return false;
 }