refactor!: module API

BREAKING CHANGE: This backports some architectural choices from v3.0.
This changes Doom's module API, renaming some functions and removing
others, in order to facilitate some new features, prepare to move Doom's
modules into separate repos, and make way for two, much larger breaking
commits coming in the next few days.

This commit won't break anything for users unless they're tinkering with
Doom's internals/using its `doom-module-*` API directly. I am avoiding
broader backwards incompatibilities until the 3.0 release.

What's new:

- Negated flags. (modulep! :editor evil -everywhere) will return non-nil
  if :editor evil is active without its +everywhere flag.
- `modulep!` now takes multiple flags to simplify AND checks. E.g.

    (and (modulep! +foo)
         (modulep! +bar)
         (not (modulep! +baz)))

  Can now be expressed with:

    (modulep! +foo +bar -baz)
- Adds pcase matchers for `doom-module-context` and `doom-module`
  structs, making the following destructuring binds possible:

    (pcase-dolist ((doom-module group name flags features)
                   (hash-table-values doom-modules))
      ...)

  This will be used more in v3.0.
- Adds file cookie support to module init.el and config.el files.

Here's a summary of breaking changes made in this commit:

- `doom-module-context` was changed from a vector to a struct (record).
- `doom-modules` is now a table of `doom-module` structs, rather than
  free-form plists.
- The following macros have been renamed:
  - `doom-context-with` -> `with-doom-context`
  - `doom-module-context-with` -> `with-doom-module`
- The followings functions have been replaced/removed:
  - `doom-module-context`+`doom-module-context-get` -> `doom-module`
  - `doom-module-set` -> `doom-module--put`
  - `doom-module-p` -> `doom-module-active-p`
  - `doom-module-context-key` (is now a getter with the same name)
  - `doom-module-put` (removed)
  - `doom-module--context-field` (removed)
- The signatures for these functions have changed:
  - `doom-module-get CATEGORY &optional MODULE PROP` ->
    `doom-module-get (GROUP . MODULE) &optional PROP`
  - `doom-module-locate-path CATEGORY &optional MODULE FILE` ->
    `doom-module-locate-path (GROUP . MODULE) &optional FILE`
  - `doom-module-expand-path CATEGORY MODULE &optional FILE` ->
    `doom-module-expand-path (GROUP . MODULE) &optional FILE`
- Adds the following functions
  - `doom-module-exists-p`
  - `doom-module-key`
  - `doom-module->context`
  - `doom-module<-context`
- Removes the following variables
  - `doom-module--empty-context`

This commit results in a little redundancy, which I will address in
parts 2/3 and/or v3.0.

lisp/lib/files.el

@@ -144,7 +144,7 @@ MATCH is a string regexp. Only entries that match it will be included."
       result)))
 
 ;;;###autoload
-(defun doom-file-cookie-p (file &optional cookie null-value)
+(defun doom-file-cookie (file &optional cookie null-value)
   "Returns the evaluated result of FORM in a ;;;###COOKIE FORM at the top of
 FILE.
 
@@ -158,11 +158,24 @@ return NULL-VALUE."
     (insert-file-contents file nil 0 256)
     (if (re-search-forward (format "^;;;###%s " (regexp-quote (or cookie "if")))
                            nil t)
-        (doom-module-context-with (doom-module-from-path file)
-          (let ((load-file-name file))
-            (eval (sexp-at-point) t)))
+        (sexp-at-point)
       null-value)))
 
+;;;###autoload
+(defun doom-file-cookie-p (file &optional cookie null-value)
+  "Returns the evaluated result of FORM in a ;;;###COOKIE FORM at the top of
+FILE.
+
+If COOKIE doesn't exist, or cookie isn't within the first 256 bytes of FILE,
+return NULL-VALUE."
+  (let ((sexp (doom-file-cookie file cookie null-value)))
+    (if (equal sexp null-value)
+        null-value
+      (with-temp-buffer
+        (with-doom-module (doom-module-from-path file)
+          (let ((load-file-name file))
+            (eval (doom-file-cookie file cookie null-value) t)))))))
+
 ;;;###autoload
 (defmacro file-exists-p! (files &optional directory)
   "Returns non-nil if the FILES in DIRECTORY all exist.