test: remove unnecessary rpc calls from feature_dbcrash #35394

On my machine dbcrash takes 17 minutes to run (wihtout --usecli), and is making on the order of 200,000 RPC calls. The bulk of these come from miniwallet's send_self_transfer_multi which calls miniwallets sendrawtransaction, which does:

    def sendrawtransaction(self, *, from_node, tx_hex, maxfeerate=0, **kwargs):
        txid = from_node.sendrawtransaction(hexstring=tx_hex, maxfeerate=maxfeerate, **kwargs)
        self.scan_tx(from_node.decoderawtransaction(tx_hex))
        return txid

The second decoderawtransaction here doubles the number of RPC calls per send, and feature_dbcrash doesn't use the miniwallet utxo list outside of setup and rescans, it already tracks it's own utxo_list, so this is wasted work.

By creating the transaction and sending using a direct node RPC to send, we can halve the number of rpc calls in this section.

This change reduces the runtime to 9 minutes for me.

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Code Coverage & Benchmarks

For details see: https://corecheck.dev/bitcoin/bitcoin/pulls/35394.

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Reviews

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nice. 40% faster for me.

review ACK c17cc76a1877a5ee5f60501eb66d0ef2e5ebfe1e 📐

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