(PUP-3642) Remove environment name from URL path

This commit makes some changes to the indirector network layer
such that the environment name is no longer a part of the main
URL path structure.  This will allow us to have a more finite URL space
and run Puppet in the same webserver with other apps, without
worrying about URL collisions.  Instead, the environment becomes a query
parameter.
Same question about environment escaping, but now that `request_to_uri_and_body` and `request_to_uri` are almost identical, can the latter call the former and join them together with `?`