Integrate Flymake elisp checkers into elisp-mode.el directly

Integrate Flymake elisp checkers into elisp-mode.el directly

* lisp/progmodes/elisp-mode.el (emacs-lisp-mode): Use
elisp-flymake-checkdoc and elisp-flymake-byte-compile.
(elisp-flymake--checkdoc-1, elisp-flymake-checkdoc)
(elisp-flymake--byte-compile-done)
(elisp-flymake--byte-compile-process)
(elisp-flymake-byte-compile): Rename from flymake-elisp
counterparts in deleted flymake-elisp.el
(elisp-flymake--batch-compile-for-flymake): New helper.
(checkdoc-create-error-function)
(checkdoc-autofix-flag)
(checkdoc-generate-compile-warnings-flag)
(checkdoc-diagnostic-buffer): Forward declare.

* lisp/progmodes/flymake-elisp.el: Delete.