Remove use of CRPCTable::appendCommand in wallet code

This commit does not change behavior.

src/wallet/test/wallet_test_fixture.cpp

@@ -15,5 +15,5 @@ WalletTestingSetup::WalletTestingSetup(const std::string& chainName):
     m_wallet.LoadWallet(fFirstRun);
     m_wallet.m_chain_notifications_handler = m_chain->handleNotifications(m_wallet);
 
-    RegisterWalletRPCCommands(tableRPC);
+    m_chain_client->registerRpcs();
 }

src/wallet/test/wallet_test_fixture.h

@@ -19,6 +19,7 @@ struct WalletTestingSetup: public TestingSetup {
     explicit WalletTestingSetup(const std::string& chainName = CBaseChainParams::MAIN);
 
     std::unique_ptr<interfaces::Chain> m_chain = interfaces::MakeChain();
+    std::unique_ptr<interfaces::ChainClient> m_chain_client = interfaces::MakeWalletClient(*m_chain, {});
     CWallet m_wallet;
 };