Further housekeeping, bring the initial load down to under 1500 ms

Make the editor load faster by deferring as much as possible until
later use. For example, LSP load is now deferred until first use and
no longer blocking.

Use only elixir-format from elixir-mode, for similar speed
reasons. The rest of the package has been taken over by the treesitter
version of the mode.

lisp/langs/icejam-lang-markdown.el

@@ -8,7 +8,7 @@
 ;; a warning from the byte compiler.
 (declare-function elpaca-installed-p "elpaca")
 (unless (elpaca-installed-p 'markdown-mode)
-  (use-package markdown-mode :ensure t))
+  (use-package markdown-mode :ensure t :defer t))
 
 (with-eval-after-load 'markdown-mode
   (setq-default markdown-command "pandoc"))