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/txdb.cpp

@@ -7,11 +7,11 @@
 
 #include <coins.h>
 #include <dbwrapper.h>
-#include <logging.h>
 #include <primitives/transaction.h>
 #include <random.h>
 #include <serialize.h>
 #include <uint256.h>
+#include <util/log.h>
 #include <util/vector.h>
 
 #include <cassert>