core+daemon: eliminate scheduler::{schedule,cancel} wrappers

Also move core/global-io.hpp to daemon/global.hpp

Refs: #4528, #4883
Change-Id: I0b99029f1a19d7451aab57099cd3303b7eb42ff3
diff --git a/tests/daemon/rib/readvertise/nfd-rib-readvertise-destination.t.cpp b/tests/daemon/rib/readvertise/nfd-rib-readvertise-destination.t.cpp
index 4967788..d3ec057 100644
--- a/tests/daemon/rib/readvertise/nfd-rib-readvertise-destination.t.cpp
+++ b/tests/daemon/rib/readvertise/nfd-rib-readvertise-destination.t.cpp
@@ -58,7 +58,7 @@
 
 protected:
   ndn::util::DummyClientFace face;
-  ndn::util::Scheduler scheduler;
+  Scheduler scheduler;
   ndn::nfd::Controller controller;
   Rib rib;
   NfdRibReadvertiseDestination dest;