Remove use of uiInterface.LoadWallet in wallet code

This also changes the uiInterface.LoadWallet signal argument type from
shared_ptr<CWallet> to unique_ptr<interfaces::Wallet> because CWallet is an
internal wallet class that shouldn't be used in non-wallet code (and also can't
be passed across process boundaries).

This commit does not change behavior.

src/interfaces/chain.cpp

@@ -6,6 +6,7 @@
 
 #include <chain.h>
 #include <chainparams.h>
+#include <interfaces/wallet.h>
 #include <net.h>
 #include <policy/fees.h>
 #include <policy/policy.h>
@@ -251,6 +252,7 @@ public:
     void initMessage(const std::string& message) override { ::uiInterface.InitMessage(message); }
     void initWarning(const std::string& message) override { InitWarning(message); }
     void initError(const std::string& message) override { InitError(message); }
+    void loadWallet(std::unique_ptr<Wallet> wallet) override { ::uiInterface.LoadWallet(wallet); }
 };
 
 } // namespace