Get call peers by federated users

[danxuliu]

Fixes #12936

Additionally:

• it updates the ping of federated users when they join the host room for consistency with the behaviour for the rest of the participants (which is unrelated to Federated call ends after some time without a local participant #12917; there the problem is that the ping is not updated in the federated server) and because it is needed for the integration tests that depend on the ping and do not have a real external signaling server (in a real environment the external signaling server updated the ping of federated users in the host server)
• it takes into account federated users when getting the actor id from the call peers in the WebUI, which is used to set the correct avatar and background (in case the actor id was not provided by signaling messages, which it should be).
  • Note that it requires Fix using signaling session ID instead of Nextcloud session ID #12961, as otherwise the peer data is not found due to using the wrong index

[SystemKeeper]

Failed test looks a bit weird: https://github.com/nextcloud/spreed/actions/runs/10384972680/job/28753120055?pr=12962#step:15:3755 - 2 sessions?

Other than that, tested with iOS and works as advertised.

[nickvergessen]

Failed test looks a bit weird: https://github.com/nextcloud/spreed/actions/runs/10384972680/job/28753120055?pr=12962#step:15:3755 - 2 sessions?

The test is about joining twice, so that is correct.
It just didn't fail so far as the first session never pinged, so it was ignored on returning. Now it's pinged when initially joining and no longer ignored.

Will adjust the expected result

[nickvergessen]

/backport to stable30