This was never used, so let's get rid of it.

Replaces the `federation_ip_range_blacklist` configuration setting with an
`ip_range_blacklist` setting with wider scope. It now applies to:

* Federation
* Identity servers
* Push notifications
* Checking key validitity for third-party invite events

The old `federation_ip_range_blacklist` setting is still honored if present, but
with reduced scope (it only applies to federation and identity servers).

Clients disconnecting before we finish processing the request happens from time
to time. We don't need to yell about it

This ended up being a bit more invasive than I'd hoped for (not helped by
generic_worker duplicating some of the code from homeserver), but hopefully
it's an improvement.

The idea is that, rather than storing unstructured `dict`s in the config for
the listener configurations, we instead parse it into a structured
`ListenerConfig` object.

Broke in #7534.

Allow REST endpoint implemnentations to raise a RedirectException, which will
redirect the user's browser to a given location.

Python will return a tuple whether there are parentheses around the returned values or not.

I'm just sick of my editor complaining about this all over the place :)

* Fix servlet metric names

Co-Authored-By: Richard van der Hoff <1389908+richvdh@users.noreply.github.com>

* Remove redundant check

* Cover all return paths