feat(ui): Revisit required_state for RoomListService

[Hywan]

This patch updates matrix_sdk_ui::room_list_service, and is twofold:

First off, it adds m.call.member, m.room.topic and m.room.pinned_events to
required_state of the all_rooms sliding sync list.

Second, this required_state sliding sync list value is easily out-of-sync with
the required_state sliding sync room subscription value. Thus, this patch
removes the settings argument of RoomListService::subscribe_to_rooms and
computes its own RoomSubscription instance. For required_state, it uses the
same required_state used by the all_rooms list, plus the m.room.create
state event. For timeline_limit, it uses 20 by default (this is not the
default value we were using in our tests, but that's the default value most
Matrix clients use).

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 84.83%. Comparing base (9c03c5d) to head (1c6399c).
Report is 5 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #4159   +/-   ##
=======================================
  Coverage   84.82%   84.83%           
=======================================
  Files         269      269           
  Lines       28862    28858    -4     
=======================================
- Hits        24482    24481    -1     
+ Misses       4380     4377    -3     

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[stefanceriu]

Talked about most of this offline, looks good to me and works well in EXI

[stefanceriu]

Best leave an explanation for this

[Hywan]

I cannot add a comment in the code, but I can comment here.

Sliding sync already supplies a response.avatar value, so we don't need to request the m.room.avatar state event.