MXS-2020 Remove maxscale/debug.h

- Removed from all files.
- maxbase/assert.h included where necessary.

server/core/event.cc

@@ -14,8 +14,8 @@
 #include "internal/event.hh"
 #include <algorithm>
 #include <string.h>
+#include <maxbase/assert.h>
 #include <maxbase/atomic.h>
-#include <maxscale/debug.h>
 
 using namespace std;