[WebUI] Add a chrome://prefs-internals page
Add a chrome://prefs-internals page that displays the JSON content of the
user's profile preferences and local state. This information is useful in
debugging when you need to know the state of a current preference.
Currently, this is particularly hard on ChromeOS, where you can't just
open the Preferences file in a text editor. This allows users to examine
preferences in the same way across platforms easily.
Add a simple page that displays this text-only information.