Major refactor of Doom core files

- Remove core-os and move many of its settings out to other core
  libraries, where they belong
- Significantly improve commenting & compartmentalization of many
  settings
- Correct some mis-named public hooks (that were named as if they were
  private)
- Move the vast majority of optimizations to "Optimizations" section in
  core.el
- Don't activate xclip-mode or osx-clipboard-mode if we're accessing
  Emacs through an SSH connection (does more bad than good there)
- Add fast-but-imprecise-scrolling = t
- Set bidi-display-reordering = 'left-to-right, at the recommendation of
  an Emacs dev. Apparently setting it to nil is undefined, as Emacs is
  designed to always assume it's set; setting it explicitly to
  left-to-right will still do what was originally intended by turning it
  off: to reduce line/text scans for bidirectional text, which gives us
  a moderate boost in general runtime snappiness
- Set inhibit-compacting-fon-caches = t on windows (where it struggles
  especially with icon fonts)
- Disables "literal" mode for very large files (because I will be
  backporting so-long.el from Emacs 27 in the next commit)

core/packages.el

@@ -4,12 +4,6 @@
 ;; core.el
 (package! dotenv-mode)
 
-;; core-os.el
-(if (not IS-MAC)
-    (package! xclip)
-  (package! osx-clipboard)
-  (package! ns-auto-titlebar))
-
 ;; core-ui.el
 (package! all-the-icons)
 (package! hide-mode-line)
@@ -26,10 +20,13 @@
 (package! command-log-mode)
 (package! dtrt-indent)
 (package! helpful)
+(package! ns-auto-titlebar :ignore (not IS-MAC))
 (package! pcre2el)
 (package! smartparens)
+(package! osx-clipboard :ignore (not IS-MAC))
 (package! undo-tree)
 (package! ws-butler)
+(package! xclip :ignore IS-LINUX)
 
 ;; core-projects.el
 (package! projectile)