[Feature] Fix race condition on subscription setup

[mattsse]

Component

provider, pubsub

Describe the feature you would like

fix for #1601 which outlined a race condition when we retrieve the subscription for the first time, this is because we drop the the rx here:

alloy/crates/pubsub/src/managers/active_sub.rs

Line 61 in b78ea8b

let (tx, _rx) = broadcast::channel(channel_size);

and by the time

let mut sub = ws_provider.root().get_subscription(sub_id).await?;

we only subscribe to new values.

alloy/crates/pubsub/src/managers/active_sub.rs

Line 74 in b78ea8b

RawSubscription { rx: self.tx.subscribe(), local_id: self.local_id }

we can fix this race in two ways

1. either change the set up in such a way that

request.set_is_subscription();
let sub_id = request.await?;

this directly awaits into a subscription

2. don't drop the receiver until the first subscription is retrieved

we can do both 1 and 2 imo, 2 should fix this issue right away

@yash-atreya

Additional context

No response