Add rebroadcast behaviour to `blockchain.transaction.broadcast`

Currently, when transactions already known to the server are rebroadcast, the server returns success but otherwise performs no additional work. The following behavioural change is proposed:

When a transaction already known to the server is rebroadcasted through blockchain.transaction.broadcast, any subscribed script hashes contained in the transaction are notified with their current script hash status.

This is primarily useful for transport level obfuscation - detection of broadcast calls may be used to identify blocks the transactions are likely to be contained in through timing analysis.

Secondarily, wallets typically need to receive these notifications to report to the user that a transaction has been successfully included in the mempool, and if they are missed due to network errors this provides a simple approach to regenerate them.

This change should be harmless to existing clients.

Start at the server implementation of the blockchain.transaction.broadcast JSON-RPC entry point and trace how subscribed script hashes receive status notifications. Ensure rebroadcasting an already-known transaction triggers notifications for its subscribed script hashes while preserving existing behavior for new transactions; verify both cases with the repository's available tests or protocol checks.