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

Jenkinsfile

@@ -124,7 +124,7 @@ def checkoutSrcs() {
 }
 
 def ClangTidy() {
-  node('linux && cpu') {
+  node('linux && cpu_build') {
     unstash name: 'srcs'
     echo "Running clang-tidy job..."
     def container_type = "clang_tidy"
@@ -239,7 +239,7 @@ def BuildCPUNonOmp() {
 }
 
 def BuildCUDA(args) {
-  node('linux && cpu') {
+  node('linux && cpu_build') {
     unstash name: 'srcs'
     echo "Build with CUDA ${args.cuda_version}"
     def container_type = "gpu_build"