[rpc] add unbroadcast info to mempool entries and getmempoolinfo

- expose info about number of txns in unbroadcast set and whether a mempool entry's tx has passed initial broadcast
- makes rpcs more informative and allows for more explicit testing, eg tracking if tx is in unbroadcast set
before and after originating node connects to peers (adds this in mempool_unbroadcast.py)
- adds mempool method IsUnbroadcastTx to query for tx inclusion in  mempool's unbroadcast set

test/functional/mempool_unbroadcast.py

@@ -53,6 +53,13 @@ class MempoolUnbroadcastTest(BitcoinTestFramework):
         txFS = node.signrawtransactionwithwallet(txF["hex"])
         rpc_tx_hsh = node.sendrawtransaction(txFS["hex"])
 
+        # check transactions are in unbroadcast using rpc
+        mempoolinfo = self.nodes[0].getmempoolinfo()
+        assert_equal(mempoolinfo['unbroadcastcount'], 2)
+        mempool = self.nodes[0].getrawmempool(True)
+        for tx in mempool:
+            assert_equal(mempool[tx]['unbroadcast'], True)
+
         # check that second node doesn't have these two txns
         mempool = self.nodes[1].getrawmempool()
         assert rpc_tx_hsh not in mempool
@@ -71,6 +78,11 @@ class MempoolUnbroadcastTest(BitcoinTestFramework):
         assert rpc_tx_hsh in mempool
         assert wallet_tx_hsh in mempool
 
+        # check that transactions are no longer in first node's unbroadcast set
+        mempool = self.nodes[0].getrawmempool(True)
+        for tx in mempool:
+            assert_equal(mempool[tx]['unbroadcast'], False)
+
         self.log.info("Add another connection & ensure transactions aren't broadcast again")
 
         conn = node.add_p2p_connection(P2PTxInvStore())