Exclude "service members" from the calculated room name when state is set in room (Implement MSC4171)

[Half-Shot]

See matrix-org/matrix-spec-proposals#4171

The purpose behind the MSC is to ensure that when you add bots such as audit bots or so on to unnamed rooms, they do not show up as part of the calculated room name (or you end up with "Alice, Bob and SurpriseBot"). The bot should show up in the member list as normal, but just not prominently in the room name.

If element-hq/synapse#17859 is implemented then in theory the heroes list will be suitable enough, but as a fallback the calculate_name() function needs to pull this state and calculate based on these rules.

It might get a bit complicated as to whether the client intends to allow support for MSC4171, as to whether these rules apply and whether the state should be fetched.

[Half-Shot]

The Synapse implementation didn't make sense in the end; For both legacy and sliding sync we can pull out (or request) the state event for service members and pass that along to the room calculation function.