Upgrade Rust SDK bindings to v25.09.15 (#5353)
* Upgrade Rust SDK bindings to `v25.09.15`:
This contains important changes to the APIs used to build the EC widget.
* Use the new `intent` parameter correctly, by calculating locally its behaviour based on whether the room is a DM and there is an ongoing call or not.
Using just the `intent` parameter is our end goal, but sadly this is not fully supported by the current EC embedded `v0.15.0`, so we need to add a workaround using the `skipLobby` and `preload` parameters.
