Unify logging facilities. (#3982)

* Unify logging facilities.

* Enhance `ConsoleLogger` to handle different verbosity.
* Override macros from `dmlc`.
* Don't use specialized gamma when building with GPU.
* Remove verbosity cache in monitor.
* Test monitor.
* Deprecate `silent`.
* Fix doc and messages.
* Fix python test.
* Fix silent tests.

tests/cpp/common/test_device_helpers.cu

@@ -5,7 +5,6 @@
 #include <thrust/device_vector.h>
 #include <xgboost/base.h>
 #include "../../../src/common/device_helpers.cuh"
-#include "../../../src/common/timer.h"
 #include "gtest/gtest.h"
 
 struct Shard { int id; };