[Move Only] Move wallet related things to src/wallet/

could once be renamed from /src/wallet to /src/legacywallet.

src/test/accounting_tests.cpp

@@ -2,8 +2,8 @@
 // Distributed under the MIT software license, see the accompanying
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
-#include "wallet.h"
-#include "walletdb.h"
+#include "wallet/wallet.h"
+#include "wallet/walletdb.h"
 
 #include "test/test_bitcoin.h"