Refactor quiet! to be less destructive

It's possible for the debugger to be invoked from inside code wrapped in
a (quiet! ...) call. The debugger pauses Emacs in a broken state where
the functions locally rebound by quiet! (e.g. message, load-file,
write-region, etc) are never returned to their original definitions.

This attempts to reduce that probabilityby changing how quiet! silences
code. Rather than silencing them completely, they will be logged
to *Messages* but not displayed in the echo area.

Also, quiet! is now used less, where it isn't strictly needed (or where
inhibit-message is sufficient).

core/test/test-autoload-files.el

@@ -40,7 +40,7 @@
       (expect (quiet! (doom/copy-this-file dest t)))
       (expect (file-exists-p! src dest)))
     (it "prompts if overwriting a file"
-      (quiet! (quiet! (doom/copy-this-file existing)))
+      (quiet! (doom/copy-this-file existing))
       (expect 'y-or-n-p :to-have-been-called-times 1)))
 
   (describe "delete-this-file"