[init] Add netgroupman to node.context

This is constructed before addrman and connman, and destructed afterwards.

netgroupman does not currently do anything, but will have functionality added in future commits.

src/node/context.cpp

@@ -9,6 +9,7 @@
 #include <interfaces/chain.h>
 #include <net.h>
 #include <net_processing.h>
+#include <netgroup.h>
 #include <policy/fees.h>
 #include <scheduler.h>
 #include <txmempool.h>