wallet: add wallet2_basic library types

The `wallet2_basic` library is a minimalistic library for loading / storing historic `wallet2` files. It has several design goals:
* Enable future migration away from monolithic `wallet2` codebase without losing funds
* Simplify FCMP++/Carrot integration
* Speed-up compile-time for current codebase, but especially the FCMP++/Carrot integration, which is split over several translation units

Co-authored-by: j-berman <justinberman@protonmail.com>
Co-authored-by: selsta <selsta@sent.at>

src/wallet/wallet2.cpp

@@ -93,6 +93,8 @@ using namespace epee;
 #include "device/device_cold.hpp"
 #include "device_trezor/device_trezor.hpp"
 #include "net/socks_connect.h"
+#include "wallet2_basic/wallet2_boost_serialization.h"
+#include "wallet2_basic/wallet2_serialization.h"
 
 extern "C"
 {