bug#53249: Context menu in other window

[Juri Linkov <juri@linkov.net>]

When clicking the right mouse button in another window,
some context-menu functions break the window configuration.
For example, when two windows show different parts of the same buffer,
this code in `prog-context-menu':

  (let ((identifier (save-excursion
                      (mouse-set-point click)
                      (xref-backend-identifier-at-point
                       (xref-find-backend)))))

moves window point of another window to the same position of the
selected window.

So the safest thing to do here is to select the window where
the context menu is invoked:

diff --git a/lisp/mouse.el b/lisp/mouse.el
index 0d8d7d6175..45b7d51da7 100644
--- a/lisp/mouse.el
+++ b/lisp/mouse.el
@@ -320,6 +320,8 @@ context-menu-map
          (fun (mouse-posn-property (event-start click)
                                    'context-menu-function)))
 
+    (select-window (posn-window (event-start click)))
+
     (if (functionp fun)
         (setq menu (funcall fun menu click))
       (run-hook-wrapped 'context-menu-functions
--