Common interface for collective communication (#8057)

* implement broadcast for federated communicator

* implement allreduce

* add communicator factory

* add device adapter

* add device communicator to factory

* add rabit communicator

* add rabit communicator to the factory

* add nccl device communicator

* add synchronize to device communicator

* add back print and getprocessorname

* add python wrapper and c api

* clean up types

* fix non-gpu build

* try to fix ci

* fix std::size_t

* portable string compare ignore case

* c style size_t

* fix lint errors

* cross platform setenv

* fix memory leak

* fix lint errors

* address review feedback

* add python test for rabit communicator

* fix failing gtest

* use json to configure communicators

* fix lint error

* get rid of factories

* fix cpu build

* fix include

* fix python import

* don't export collective.py yet

* skip collective communicator pytest on windows

* add review feedback

* update documentation

* remove mpi communicator type

* fix tests

* shutdown the communicator separately

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

plugin/federated/federated.proto

@@ -12,16 +12,14 @@ service Federated {
 }
 
 enum DataType {
-  CHAR = 0;
-  UCHAR = 1;
-  INT = 2;
-  UINT = 3;
-  LONG = 4;
-  ULONG = 5;
+  INT8 = 0;
+  UINT8 = 1;
+  INT32 = 2;
+  UINT32 = 3;
+  INT64 = 4;
+  UINT64 = 5;
   FLOAT = 6;
   DOUBLE = 7;
-  LONGLONG = 8;
-  ULONGLONG = 9;
 }
 
 enum ReduceOperation {