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

src/wallet/rpc/wallet.cpp

@@ -18,6 +18,7 @@
 #include <univalue.h>
 
 
+namespace wallet {
 /** Checks if a CKey is in the given CWallet compressed or otherwise*/
 bool HaveKey(const SigningProvider& wallet, const CKey& key)
 {
@@ -729,3 +730,4 @@ static const CRPCCommand commands[] =
 // clang-format on
     return commands;
 }
+} // namespace wallet