Integrate elisp checkers into elisp-mode.el directly

Integrate 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.

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