Add src/wallet/* code to wallet:: namespace

src/wallet/walletdb.cpp

@@ -26,6 +26,7 @@
 #include <optional>
 #include <string>
 
+namespace wallet {
 namespace DBKeys {
 const std::string ACENTRY{"acentry"};
 const std::string ACTIVEEXTERNALSPK{"activeexternalspk"};
@@ -1194,3 +1195,4 @@ std::unique_ptr<WalletDatabase> CreateMockWalletDatabase()
     return std::make_unique<BerkeleyDatabase>(std::make_shared<BerkeleyEnvironment>(), "");
 #endif
 }
+} // namespace wallet