Tab for list of calls with bridged users

### Your use case

In an environment where the user has the ability to start outgoing calls or receive incoming calls from a non-matrix network from non-matrix users (typically Numbers from a PSTN network) via a bridge device, it is beneficial to separate the rooms created with these bridged users in its own list of calls. This is because the available interactions with these non-matrix users are different than with matrix-users and the management of direct contacts is kept simple by not having them polluted by this kind of rooms.

This list of calls should be shown depending of the availability of a PSTN bridge.

Design aspects:
As the PSTN bridge creates a matrix user as a proxy for each PSTN number, it would be needed to distinguish this kind of special matrix user from a normal matrix user. Based on the presence of such a special matrix user within a room, the room itself can then be considered a "call" room to be presented in the call list and be excluded from being presented in the list of direct rooms or group rooms.

Created a video for demonstration purpose:
(https://aarenet-my.sharepoint.com/:v:/p/simon_wiedmer/ERSzUmOQMTRPhFjJfvFndxIBh_NBh2PBogLvOzCfPMHgRA?e=GrQwRb)

The issue names no files, tests, or entry points. Start by locating the iOS room-list and PSTN-bridge user handling, then confirm how bridge availability and special proxy users should affect room classification. Done means the separate call list is shown when appropriate and those rooms are excluded from direct and group room lists.

Written by the indexing model from the issue text.