fees: refactor: rename fees to block_policy_estimator

- Also move it to policy/fees and update the includes

src/wallet/interfaces.cpp

@@ -9,7 +9,7 @@
 #include <interfaces/chain.h>
 #include <interfaces/handler.h>
 #include <node/types.h>
-#include <policy/fees.h>
+#include <policy/fees/block_policy_estimator.h>
 #include <primitives/transaction.h>
 #include <rpc/server.h>
 #include <scheduler.h>