GPU implementation of AFT survival objective and metric (#5714)

* Add interval accuracy

* De-virtualize AFT functions

* Lint

* Refactor AFT metric using GPU-CPU reducer

* Fix R build

* Fix build on Windows

* Fix copyright header

* Clang-tidy

* Fix crashing demo

* Fix typos in comment; explain GPU ID

* Remove unnecessary #include

* Add C++ test for interval accuracy

* Fix a bug in accuracy metric: use log pred

* Refactor AFT objective using GPU-CPU Transform

* Lint

* Fix lint

* Use Ninja to speed up build

* Use time, not /usr/bin/time

* Add cpu_build worker class, with concurrency = 1

* Use concurrency = 1 only for CUDA build

* concurrency = 1 for clang-tidy

* Address reviewer's feedback

* Update link to AFT paper

amalgamation/xgboost-all0.cc

@@ -76,7 +76,6 @@
 #include "../src/common/json.cc"
 #include "../src/common/io.cc"
 #include "../src/common/survival_util.cc"
-#include "../src/common/probability_distribution.cc"
 #include "../src/common/version.cc"
 
 // c_api