Doc strings, `declare` and `interactive` forms must appear in that
order and at most once each. Complain if they don't, instead of
silently ignoring the problem (bug#55905).
* lisp/emacs-lisp/byte-run.el (byte-run--parse-body)
(byte-run--parse-declarations): New.
(defmacro, defun): Check for declaration well-formedness as
described above. Clarify doc strings. Refactor some common code.
* test/lisp/emacs-lisp/bytecomp-resources/fun-attr-warn.el:
* test/lisp/emacs-lisp/bytecomp-tests.el (bytecomp-fun-attr-warn):
New test.
