(cl-types-of): Speed up by caching more of its work

(cl-types-of): Speed up by caching more of its work

* lisp/emacs-lisp/cl-types.el (cl--type-parents): Make it a proper function.
(cl--type-children): Use `cl--class-children` and make it a `defsubst`.
(cl--type-dag): η-reduce and make it a `defsubst`.
(cl--type-undefine): Also reset `cl--type-error`.
(cl--type-deftype): Modify `cl--type-list` atomically so we never need
to restore it upon error.  Don't test bogus parent here.
(cl-deftype2): Test bogus parent here instead.  Also, better preserve
the declarations for the lambda.
(cl-types-of): Do less uncached work.

(cherry picked from commit 4323ff209f2f73ca4e6d389de69eb310988c0b1f)