Fix insertion of keyboard macro containing named keys

Fix insertion of keyboard macro containing named keys

* lisp/kmacro.el: Autoload `macro--string-to-vector'.
(kmacro-ring-head): Convert `last-kbd-macro' to a vector if it's a
string, since `kmacro' uses `key-parse' on it.
(kmacro-lambda-form): Remove require for 'macros
* test/lisp/kmacro-tests.el
(kmacro-tests-name-last-macro-key-parse-syntax):
Test that insertion of macros that contain strings that look
like named keys works correctly.

(Bug#61700)