Fix when_known not notified

[tomaka]

Fixed a bug introduced in #2180

Before #2180, we were detecting when the runtime is ready by subscribing to notifications about the chain, and then reading the state again when something happens on this subscription.
This is hacky, so I replaced it with a when_known: EventListener that gets notified when the runtime is ready.

Unfortunately, I forgot to notify this EventListener in case the sync service notification resets.

The problematic situation is:

• You call RuntimeService::subscribe_all at the very beginning. The runtime service is in the FinalizedBlockRuntimeUnknown state, and we listen for events on the when_ready.
• The sync service finishes its warp sync, and resets all its notifications subscribers.
• This causes the RuntimeService to reset and to re-subscribe to the sync service.
• Because the sync service has a runtime already ready, we immediately transition to FinalizedBlockRuntimeKnown, but without notifying the when_ready. This is what this PR fixes.

Because some JSON-RPC functions indirectly rely on RuntimeService::subscribe_all, this bug causes these JSON-RPC functions to never produce any answer if they are called at the very beginning.

[mergify]

Automatically approving tomaka's pull requests. This auto-approval will be removed once more maintainers are active.

[github-actions]

twiggy diff report

Difference in .wasm size before and after this pull request.

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 Delta Bytes │ Item
─────────────┼──────────────────────────────────────────────────────────────────────────────────────────────────────
         +30 ┊ <core::future::from_generator::GenFuture<T> as core::future::future::Future>::poll::hacaa93e948fa8839
         +30 ┊ Σ [1 Total Rows]

[melekes]

👍