refactor: use doom-module-*-file variables; add two

- Adds doom-module-packages-file and doom-module-metadata-file.
- Uses them and the other doom-module-*-file variables where they were
  previously hardcoded.
- Add .el extension to doom-module-{init,config}-file; it is now the
  consumer's responsibility to strip/change/keep the extension as they
  see fit.

lisp/lib/config.el

@@ -34,7 +34,7 @@
   "Open your private init.el file.
 And jumps to your `doom!' block."
   (interactive)
-  (find-file (expand-file-name "init.el" doom-user-dir))
+  (find-file (expand-file-name doom-module-init-file doom-user-dir))
   (goto-char
    (or (save-excursion
          (goto-char (point-min))
@@ -45,13 +45,13 @@ And jumps to your `doom!' block."
 (defun doom/goto-private-config-file ()
   "Open your private config.el file."
   (interactive)
-  (find-file (expand-file-name "config.el" doom-user-dir)))
+  (find-file (expand-file-name doom-module-config-file doom-user-dir)))
 
 ;;;###autoload
 (defun doom/goto-private-packages-file ()
   "Open your private packages.el file."
   (interactive)
-  (find-file (expand-file-name "packages.el" doom-user-dir)))
+  (find-file (expand-file-name doom-module-packages-file doom-user-dir)))
 
 
 ;;

lisp/lib/debug.el

@@ -331,7 +331,7 @@ ready to be pasted in a bug report on github."
          ,@(condition-case e
                (mapcar
                 #'cdr (doom--collect-forms-in
-                       (doom-path doom-user-dir "packages.el")
+                       (doom-path doom-user-dir doom-module-packages-file)
                        "package!"))
              (error (format "<%S>" e))))
         (unpin
@@ -339,7 +339,7 @@ ready to be pasted in a bug report on github."
                (mapcan #'identity
                        (mapcar
                         #'cdr (doom--collect-forms-in
-                               (doom-path doom-user-dir "packages.el")
+                               (doom-path doom-user-dir doom-module-packages-file)
                                "unpin!")))
              (error (list (format "<%S>" e)))))
         (elpa

lisp/lib/packages.el

@@ -162,7 +162,7 @@ each package."
            (ignore-errors (intern (cadr module)))
            current-prefix-arg)))
   (mapc (lambda! ((cat . mod))
-          (if-let (packages-file (doom-module-locate-path cat mod "packages.el"))
+          (if-let (packages-file (doom-module-locate-path cat mod doom-module-packages-file))
               (with-current-buffer
                   (or (get-file-buffer packages-file)
                       (find-file-noselect packages-file))
@@ -185,7 +185,7 @@ each package."
     (unless modules
       (user-error "This package isn't installed by any Doom module"))
     (dolist (module modules)
-      (when-let (packages-file (doom-module-locate-path (car module) (cdr module)))
+      (when (doom-module-locate-path (car module) (cdr module) doom-module-packages-file)
         (doom/bump-module (car module) (cdr module))))))