Standardize REPL commands & improve SPC o r

- SPC o r now prompts for a REPL to open when none was found for the
  current buffer.
- REPL handlers must now follow the naming convention "*/open*-repl".
  e.g. +python/open-ipython-repl, +emacs-lisp/open-repl, etc.
- +eval/open-repl has been split in two:
  - +eval/open-repl-other-window
  - +eval/open-repl-same-window

modules/lang/lua/config.el

@@ -15,7 +15,7 @@
   :config
   (set-lookup-handlers! 'lua-mode :documentation 'lua-search-documentation)
   (set-electric! 'lua-mode :words '("else" "end"))
-  (set-repl-handler! 'lua-mode #'+lua/repl)
+  (set-repl-handler! 'lua-mode #'+lua/open-repl)
   (set-company-backend! 'lua-mode '(company-lua company-yasnippet)))