cond-star: Fix trivial typos, checkdoc fixes, etc.

cond-star: Fix trivial typos, checkdoc fixes, etc.

* lisp/emacs-lisp/cond-star.el (cond*):
Add header and footer as per checkdoc fixes.

(match*, cond*-non-exit-clause-substance)
(cond*-convert-clause, cond*-convert-condition)
(cond*-match, cond*-subpat)
(cond*-used-within, cond-star):
Fix typos in comments, and apply checkdoc fixes.  (Bug#72546)

(cherry picked from commit 4197a8450669e08c2d26f4a7d77dcb2771bd9492)