authority-discovery: Support multiple authority ids per peer id (#10259)

* authority-discovery: Support multiple authority ids per peer id

An peer id can be mapped to multiple authority ids, because an authority id is a session key that
could be changed every session. Before this pr the internal authority discovery cache assumed that
each authority id can only be mapped to one peer id. However, this isn't true since we changed the
default implementation of the authority discovery to combine the current and next session authorities.

* Review feedback

* Update client/authority-discovery/src/worker/addr_cache.rs

Co-authored-by: Andronik Ordian <write@reusable.software>

* Early return on no peer ids

* Update client/authority-discovery/src/worker/addr_cache.rs

Co-authored-by: Pierre Krieger <pierre.krieger1708@gmail.com>

* Update types in comment

* FMT

* Add warning

* Update client/authority-discovery/src/worker/addr_cache.rs

Co-authored-by: Andronik Ordian <write@reusable.software>

* Feedback

Co-authored-by: Andronik Ordian <write@reusable.software>
Co-authored-by: Pierre Krieger <pierre.krieger1708@gmail.com>