Refactor element call lobby + skip lobby

[toger5]

This PR can be reviewed per commit:

• The first commit updates the embedding to use the lobby that is supported by Element Call (instead of the custom EW lobby). We also update the EC url generation to use template variables. (this allows to store the configuration in widget.data which makes it easy to parse the current widget configuration.
• The second commit hooks up various places where one can join/start a call so that shiftKey+click will skip the lobby.
• The last commit removes all the code that is not needed anymore. (Lobby UI)

All the following commits refactor and add a lot of testing changes.
Signed-off-by: Timo K toger5@hotmail.de
Requires: element-hq/element-web#26879

Alert

In its current state this breaks Jitsi (because its removing the lobby code entirely)

Checklist

• Tests written for new code (and old code if feasible)
• Linter and other CI checks pass
• Sign-off given on the changes (see CONTRIBUTING.md)

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Here's what your changelog entry will look like:

✨ Features

• Refactor element call lobby + skip lobby (#12057). Contributed by @toger5.

[robintown]

I was able to follow this for the most part, but the one part I need reminding about is why we need to use the 'connected' state for simply viewing the lobby

[robintown]

Non-blocking comment: I just had the thought that these two fields could be combined in a single view_call?: "lobby" | "call" field, for the sake of keeping related data together. Otherwise you end up with { action: "view_room", view_call: undefined, skipLobby: true } as a possible payload, which isn't very meaningful IMO.

[toger5]

I see the redundance in the information (4 casses for 3 possible scenarios)
I thought about it for a bit but for the sake of intruducing fewer termonology I think we should keep it for now.
skipLobby is a documented term also in EC. intrducing "view_room":"lobby" would need everyone to understand that this results in skipLobby=true.

So if we fix this it should be fixed for the whole chain: EC would need to get a view property which an be set to "lobby" or `"call".
WDYT?

[robintown]

Hmm, I do see the value in having the terms be consistent. Maybe we could go with view_call?: "lobby" | "skipLobby" to keep the connection there without needing to change how EC handles this flag?

[toger5]

That reduces the possible inputs to 3 (which makes sense sicne there are only 3 possible choices)

It is slighly harder to read (a bit more confusing) in the case there is a running call and its just about showing that call. In this case one need to set it to "lobby" but just wants to show the running call.
And undefined would mean it deos NOT show the call (moves the call to pip)

[toger5]

Is there something like rust enums:

enum ViewCallSettings{
    ViewCall(LobbySetting),
    UnViewCall,
    Keep,
}
enum LobbySetting{
    Skip,
    Show,
    Default
}

Its really 5 cases in the end:

• view call with whatever lobby setting is the default
• view call with in lobby state
• view call and skip the lobby
• Explicitly dont view the call but instead the caht
• dispatch a roomView update but dont touch the view call settings