Allow using peer-to-peer for one-on-one video chat

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Feature request

Which Nextcloud Version are you currently using: (see administration page)
29.0.5

Is your feature request related to a problem? Please describe.
When creating one-on-one video connections with a configured high performance backend plus video bridge (i.e. janus) the video is always routed through the janus bridge even though the clients don't have any additional benefit from that (given that they can connect to each other directly).

Describe the solution you'd like
I'd like to have the option to first try peer-to-peer connections for those one-on-one video chats to keep the bridge load to a minimum and use it only when its necessary for larger conferences.

Jitsi for example uses this technique to keep the server load low.

Describe alternatives you've considered
Depending on the typical load for the server one could just as well disable the janus gateway which would in turn make larger conferences problematic for the clients.

Additional context
I also made this request in the nextcloud-spreed-signaling project where I was redirected here, see https://github.com/strukturag/nextcloud-spreed-signaling/issues/804

Thanks for the attention and NC Talk!

Review the existing one-on-one call routing and Janus signaling flow, along with the related nextcloud-spreed-signaling issue 804. Determine how a peer-to-peer attempt can be negotiated before bridge use and how fallback should work. Done means one-on-one calls prefer direct connections while larger conferences continue using the bridge.