(cl-labels): Add support for (FUNC EXP) bindings (bug#59786)

(cl-labels): Add support for (FUNC EXP) bindings (bug#59786)

Allow `cl-labels` to use the same (FUNC EXP) bindings as were already added
to `cl-flet` in Emacs-25.  The Info doc (mistakenly) already documented this
new feature.

* lisp/emacs-lisp/cl-macs.el (cl--self-tco-on-form): New function.
(cl-labels): Use it to add support for (FUNC EXP) bindings.

* test/lisp/emacs-lisp/cl-macs-tests.el (cl-macs--labels): Add test for
tail-recursive (FUNC EXP) bindings.

(cherry picked from commit 79400f4f18b80cdde72eda86023e41a81d09a164)