logging: use util/log.h where possible

Preparation for a future commit where kernel's dependency
on logging.cpp is removed completely.

Replace usage of logging\.h with util/log\.h where it
suffices, and fix wrong includes according to iwyu.

src/sync.cpp

@@ -4,8 +4,8 @@
 
 #include <sync.h>
 
-#include <logging.h>
 #include <tinyformat.h>
+#include <util/log.h>
 #include <util/strencodings.h>
 #include <util/threadnames.h>