Merge bitcoin/bitcoin#22510: test: add test for RPC error 'Transaction already in block chain'

2ebf2fe0e4 test: check for RPC error 'Transaction already in block chain' (-27) (Sebastian Falbesoner)

Pull request description:

  This PR adds missing test coverage for the RPC error "Transaction already in block chain" (error code `RPC_VERIFY_ALREADY_IN_CHAIN` = `RPC_TRANSACTION_ALREADY_IN_CHAIN` = -27), which is thrown in the function `BroadcastTransaction` (src/node/transaction.cpp).

ACKs for top commit:
  kristapsk:
    ACK 2ebf2fe0e4 (ran linter, looked at changes and ran modified test and checked code in `src/node/transaction.cpp`)
  darosior:
    ACK 2ebf2fe0e4

Tree-SHA512: 8bfbd3ff3da0cb3b8745f69b8ca2377f85fa99f0270750840b60e6ae43b5645c5c59b236993e8b2ad0444ec4171484e4f1ee23fa7e81b79d4222bcb623666fa5

test/functional/rpc_rawtransaction.py

@@ -515,6 +515,15 @@ class RawTransactionsTest(BitcoinTestFramework):
         assert_equal(testres['allowed'], True)
         self.nodes[2].sendrawtransaction(hexstring=rawTxSigned['hex'], maxfeerate='0.20000000')
 
+        self.log.info('sendrawtransaction/testmempoolaccept with tx that is already in the chain')
+        self.nodes[2].generate(1)
+        self.sync_blocks()
+        for node in self.nodes:
+            testres = node.testmempoolaccept([rawTxSigned['hex']])[0]
+            assert_equal(testres['allowed'], False)
+            assert_equal(testres['reject-reason'], 'txn-already-known')
+            assert_raises_rpc_error(-27, 'Transaction already in block chain', node.sendrawtransaction, rawTxSigned['hex'])
+
 
 if __name__ == '__main__':
     RawTransactionsTest().main()