refactor: introduce doom-module-context

Where f9201eb introduced a general context system, this one introduces
one for modules, to simplify our let-bind game when interacting with
modules, and to more efficiently expose module state to modulep! (which
gets called at runtime a great deal, so its performance is important).

* lisp/doom-lib.el (doom-log): simplify macro and introduce
  doom-inhibit-log variable.
* lisp/doom-modules.el (modulep!): fix reported file path if modulep!
  fails to find the local module.
* lisp/lib/debug.el (doom-debug-variables): disable doom-inhibit-log
  when debug mode is on.

Ref: f9201eb218

lisp/lib/debug.el

@@ -9,6 +9,7 @@
 (defvar doom-debug-variables
   `(;; Doom variables
     (doom-print-minimum-level . debug)
+    (doom-inhibit-log . nil)
 
     ;; Emacs variables
     async-debug