Factored out into #12193.

to_key prevents overlapping bounds when pulling out device list updates.

user_ids needs to be optional as we won't have a list of user_ids to
filter with when calling this function from a triggered device_list
change.

So that we can use it elsewhere.

In the next commit, we'll be merging one DeviceList into another. This
will require the ability to remove items by value, which Collection does
not provide, while a mutable structure such as Set does. Set was chosen to
to remove duplicate user IDs.

…iven AS

When a new device list change occurs, we're now:

1. For each appservice, checking the last device list stream key that was
   processed up until.
2. Getting any users with changed device list between the last device list
   stream key and the stream key of the triggering update.
3. Filtering out those users based on those that are actually relevant
   to this application service.
4. Passing those changes to enqueue_for_appservice and saving the device list
   stream key that we've just processed up to for later reference.

Here we implement code that adds support for device list changes all
the way from our enqueue_for_appservice method down to where AS
transactions are actually built and sent out.

Mainly just adding device list parameters to every method call.

We add a series of tests that check whether device list sending works
across a variety of possible configurations.

Co-authored-by: Patrick Cloke <clokep@users.noreply.github.com>

…_as_device_lists

Co-authored-by: Patrick Cloke <clokep@users.noreply.github.com>

…_as_device_lists

This makes mypy happy!

…_as_device_lists

…_as_device_lists