[Breaking] Switch from rabit to the collective communicator (#8257)

* Switch from rabit to the collective communicator

* fix size_t specialization

* really fix size_t

* try again

* add include

* more include

* fix lint errors

* remove rabit includes

* fix pylint error

* return dict from communicator context

* fix communicator shutdown

* fix dask test

* reset communicator mocklist

* fix distributed tests

* do not save device communicator

* fix jvm gpu tests

* add python test for federated communicator

* Update gputreeshap submodule

Co-authored-by: Hyunsu Philip Cho <chohyu01@cs.washington.edu>

src/common/hist_util.cc

@@ -3,19 +3,14 @@
  * \file hist_util.cc
  */
 #include <dmlc/timer.h>
-#include <dmlc/omp.h>
 
-#include <rabit/rabit.h>
-#include <numeric>
 #include <vector>
 
 #include "xgboost/base.h"
 #include "../common/common.h"
 #include "hist_util.h"
-#include "random.h"
 #include "column_matrix.h"
 #include "quantile.h"
-#include "../data/gradient_index.h"
 
 #if defined(XGBOOST_MM_PREFETCH_PRESENT)
   #include <xmmintrin.h>