refactor!(elixir): remove alchemist

BREAKING CHANGE: alchemist appears to be unmaintained and has reportedly
been replaced by elixir-ls and LSP (#5488). To restore your Elixir dev
environemnt, enable :lang (elixir +lsp) and install elixir-ls via your
package manager or 'M-x lsp-install-server'.

Close: #5488

modules/lang/elixir/config.el

@@ -56,39 +56,6 @@
   :config (flycheck-credo-setup))
 
 
-(use-package! alchemist
-  :hook (elixir-mode . alchemist-mode)
-  :config
-  (set-lookup-handlers! 'elixir-mode
-    :definition #'alchemist-goto-definition-at-point
-    :documentation #'alchemist-help-search-at-point)
-  (set-eval-handler! 'elixir-mode #'alchemist-eval-region)
-  (set-repl-handler! 'elixir-mode #'alchemist-iex-project-run)
-  (map! :after elixir-mode
-        :localleader
-        :map elixir-mode-map
-        "m" #'alchemist-mix
-        "c" #'alchemist-mix-compile
-        "i" #'alchemist-iex-project-run
-        "f" #'elixir-format
-        (:prefix ("e" . "eval")
-         "e" #'alchemist-iex-send-last-sexp
-         "r" #'alchemist-iex-send-region
-         "l" #'alchemist-iex-send-current-line
-         "R" #'alchemist-iex-reload-module)))
-
-
-(use-package! alchemist-company
-  :when (modulep! :completion company)
-  :commands alchemist-company
-  :config
-  (set-company-backend! 'alchemist-mode '(alchemist-company company-yasnippet))
-  ;; Alchemist doesn't use hook symbols to add these backends, so we have to use
-  ;; the entire closure to get rid of it.
-  (let ((fn (byte-compile (lambda () (add-to-list (make-local-variable 'company-backends) 'alchemist-company)))))
-    (remove-hook 'alchemist-mode-hook fn)
-    (remove-hook 'alchemist-iex-mode-hook fn)))
-
 (use-package! exunit
   :hook (elixir-mode . exunit-mode)
   :init