[net] Rename the copyStats arg from m_asmap to asmap

The m_ prefix indicates that a variable is a data member. Using it as
a parameter name is misleading.

Also update the name of the function from copyStats to CopyStats to
comply with our style guide.

src/test/fuzz/net.cpp

@@ -46,7 +46,7 @@ FUZZ_TARGET_INIT(net, initialize_net)
                     return;
                 }
                 CNodeStats stats;
-                node.copyStats(stats, asmap);
+                node.CopyStats(stats, asmap);
             },
             [&] {
                 const CNode* add_ref_node = node.AddRef();