Allow toggling completion modes for `M-x' with `M-X'

Allow toggling completion modes for `M-x' with `M-X'

* doc/lispref/commands.texi (Interactive Call): Document it.
* lisp/minibuffer.el (minibuffer-local-must-match-map): Bind 'M-X'.

* lisp/simple.el (execute-extended-command-cycle): New command.
(read-extended-command): Use it to allow toggling (bug#47215).
(read-extended-command-1): Renamed from `read-extended-command'.
(execute-extended-command-for-buffer): Factored out most of the
code...
(command-completion--command-for-this-buffer-function): ... to
here.
(extended-command-versions): New variable.

This code is based on a patch by Felician Nemeth
<felician.nemeth@gmail.com>.