refactor!: restructure Doom core

BREAKING CHANGE: This restructures the project in preparation for Doom
to be split into two repos. Users that have reconfigured Doom's CLI
stand a good chance of seeing breakage, especially if they've referred
to any core-* feature, e.g.

  (after! core-cli-ci ...)

To fix it, simply s/core-/doom-/, i.e.

  (after! doom-cli-ci ...)

What this commit specifically changes is:
- Renames all core features from core-* to doom-*
- Moves core/core-* -> lisp/doom-*
- Moves core/autoloads/* -> lisp/lib/*
- Moves core/templates -> templates/

Ref: #4273

bin/doomscript

@@ -40,7 +40,7 @@ tmpfile="$TMPDIR/doomscript.${__DOOMPID}"
 
 target="$1"
 shift
-$emacs --load "$EMACSDIR/core/core-cli" \
+$emacs --load "$EMACSDIR/lisp/doom-cli" \
        --load "$target" \
        -- "$@" || exit=$?
 # Execute exit-script, if requested (to simulate execve)