refactor: Visual indentation guides

- Switch from highlight-indentation package to highlight-indent-guides.
- Activate visual indentation in a prog-mode hook, rather than doing
  within each individual major mode. It was already done within all
  major modes based on prog-mode anyway.
- Add new siren-display-indetation module and function as a central way
  to enable visual indetation guides. This makes switching the
  underlying package at some point in the future much easier.

modules/languages/siren-lua.el

@@ -15,7 +15,6 @@
     (setq lua-indent-level 2
           whitespace-action '(auto-cleanup))
 
-    (highlight-indentation-current-column-mode)
     (subword-mode +1)))
 
 (provide 'siren-lua)