[RPC, Wallet] Move RPC dispatch table registration to wallet/ code

Allow extending the rpc dispatch table by appending commands when server is not running.

src/zcbenchmarks.cpp

@@ -431,6 +431,9 @@ double benchmark_connectblock_slow()
     return duration;
 }
 
+extern UniValue getnewaddress(const UniValue& params, bool fHelp); // in rpcwallet.cpp
+extern UniValue sendtoaddress(const UniValue& params, bool fHelp);
+
 double benchmark_sendtoaddress(CAmount amount)
 {
     UniValue params(UniValue::VARR);