This removes the ability for the client to filter remote room
directories by network, since the /thirdparty/protocols API does
not yet work for remote servers. They would only get the main list
now though anyway, so there is no point in us continuing to support
it.
As per https://github.com/matrix-org/synapse/pull/1676
The existing local config system still exists and is used for
remote home server directories (since /thirdparty/protocols
doesn't support listing remote home servers, and also because
people are using it).
Use the 3rd party location lookup API to accept third-party locations
in their native form and look up the corresponding portal room for
that location.
Also give the network dropdown some placeholder text.
Fixes https://github.com/vector-im/vector-web/issues/2374
Changes filtering on 3rd party networks to divide into portal / non portal rooms and not show portal rooms by default. Adds a special '_matrix' network for all rooms that aren't portal rooms.
Also adds ability to query 3rd party directory servers.
