RPC node's send_transaction() doesn't retry

[garious]

Problem

Same problem as #9400, but creating a separate ticket with reduced scope.

Proposed Solution

Add a thread to the RPC node that resends transactions until its blockhash expires.

[mvines]

Duplicate of #9401

[garious]

Not a duplicate. RpcClient::send_transaction() should remain non-blocking. No client-side changes needed.

[aeyakovenko]

While the RPC node is retrying, the leader should make a best effort to send back the signature + status code to the RPC node if the transaction failed in such a way that it won't be encoded into the ledger.

[mvines]

While the RPC node is retrying, the leader should make a best effort to send back the signature + status code to the RPC node if the transaction failed in such a way that it won't be encoded into the ledger.

The new sendTransaction preflight checks should mitigate most of this concern, as they will filter out invalid transactions and most execution errors.