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

src/node/chainstate.cpp

@@ -8,6 +8,7 @@
 #include <node/blockstorage.h>
 #include <validation.h>
 
+namespace node {
 std::optional<ChainstateLoadingError> LoadChainstate(bool fReset,
                                                      ChainstateManager& chainman,
                                                      CTxMemPool* mempool,
@@ -156,3 +157,4 @@ std::optional<ChainstateLoadVerifyError> VerifyLoadedChainstate(ChainstateManage
 
     return std::nullopt;
 }
+} // namespace node