Search Editor's openLocationToSide should also work right-to-left

[pkaminski]

When I have a two column editor layout and Search > Search Editor: Double Click Behaviour is set to openLocationToSide, it works well if the search editor is in the left column, opening the target on the right. If the search editor is on the right, though, it splits the pane further and messes up the layout. Instead, it should open the target in the group to its left.

This was originally reported by @dwelle in #23931 (comment), and apparently would require a modification to editor.action.openDeclarationToTheSide to consider other groups before creating a new one.