Remove the remaining fee estimation globals

This moves the CBlockPolicyEstimator to the NodeContext, which get rids
of two globals and allows us to conditionally create the
CBlockPolicyEstimator (and to remove a circular dep).

Signed-off-by: Antoine Poinsot <darosior@protonmail.com>

src/node/context.cpp

@@ -8,6 +8,7 @@
 #include <interfaces/chain.h>
 #include <net.h>
 #include <net_processing.h>
+#include <policy/fees.h>
 #include <scheduler.h>
 #include <txmempool.h>