When starting a full-node, validate the local transactions in a thread and let twisted's main loop runs

Currently, when we start a full-node, all local transactions are verified before entering into twisted's main loop.

We can validate the local transactions in a thread after entering twisted's main loop. The primary advantage is that we can use the HTTP API + WebSocket to follow the initialization.

Start at the full-node startup path where local transactions are verified before Twisted's main loop begins. Trace how validation, the HTTP API, and WebSocket initialization interact. Done means local transaction validation runs in a thread after the main loop starts, while the HTTP API and WebSocket can report initialization progress.

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