WidgetDriver: Use matrix_sdk_common::executor::spawn instead of tokio::spawn to make it wasm compatible.

[toger5]

Using the executer::spawn will select tokio::spawn or wasm_bindgen_futures::spawn_local based on what platform we are on.

They behave differently in that tokio actually starts the async block inside the spawn but the wasm spawn wrapper will only start the part that is not inside the async block and the join handle needs to be awaited for it to work.

• Public API changes documented in changelogs (optional)

Signed-off-by:

[toger5]

I think I need help on this since this is not the correct solution. When running on a non wasm platform the await will block.
So there seems to be an issue with

#[cfg(target_arch = "wasm32")]
pub fn spawn<F, T>(future: F) -> JoinHandle<T>
where
    F: Future<Output = T> + 'static,
{
    let (future, remote_handle) = future.remote_handle();
    let (abort_handle, abort_registration) = AbortHandle::new_pair();
    let future = Abortable::new(future, abort_registration);

    wasm_bindgen_futures::spawn_local(async {
        // Poll the future, and ignore the result (either it's `Ok(())`, or it's
        // `Err(Aborted)`).

        let _ = future.await;
    });
    let j = JoinHandle { remote_handle: remote_handle, abort_handle };
    j.
}

Where we need to await the JoinHandle before the future is actually started on WASM.