refactor(lib): tidy doom-log output

This commit reduces the debug log noise, makes it easier to
read/parse/search, and soft-introduces a convention for doom-log
messages, where they are prefixed with a unique identifier loosely named
after it's running context or calling function.

I haven't enforced it everywhere doom-log is used yet, but this is a
start.

lisp/cli/env.el

@@ -125,8 +125,8 @@ Why this over exec-path-from-shell?
                     (pred (doom-rpartial #'string-match-p var)))
                (when (seq-find pred denylist)
                  (if (seq-find pred allowlist)
-                     (doom-log "Whitelisted %s" var)
-                   (doom-log "Ignored %s" var)
+                     (doom-log "cli:env: allow %s" var)
+                   (doom-log "cli:env: deny %s" var)
                    (throw 'skip t)))
                (insert (prin1-to-string env) "\n "))))
          (insert ")"))