rpc/wallet: add simulaterawtransaction RPC

This command iterates over the inputs and outputs of the given transactions, and tallies up the balance change for the given wallet. This can be useful e.g. when verifying that a coin join like transaction doesn't contain unexpected inputs that the wallet will then sign for unintentionally.

src/rpc/client.cpp

@@ -147,6 +147,8 @@ static const CRPCConvertParam vRPCConvertParams[] =
     { "sendall", 1, "conf_target" },
     { "sendall", 3, "fee_rate"},
     { "sendall", 4, "options" },
+    { "simulaterawtransaction", 0, "rawtxs" },
+    { "simulaterawtransaction", 1, "options" },
     { "importprivkey", 2, "rescan" },
     { "importaddress", 2, "rescan" },
     { "importaddress", 3, "p2sh" },