This adds a prompt whenever we are about to perform some action on a default identity
server (from homeserver .well-known or Riot app config) without terms. This
allows the user to abort or trust the server (storing it in account data).
Fixes https://github.com/vector-im/riot-web/issues/10557
This allows those who previously disconnected from an IS to either choose the
default IS or a custom one from Settings via the address picker dialog.
Part of https://github.com/vector-im/riot-web/issues/10619