Add datagen for testing string-based categorical data. #11517

Job	Run time
Build libxgboost4j.dylib for MacOS (Apple Silicon)	1m 30s
Build libxgboost4j.dylib for MacOS (Intel)	2m 53s
Build libxgboost4j.so with CUDA	6m 18s
Build libxgboost4j.so targeting glibc 2.17 (arch aarch64, runner linux-arm64-cpu)	1m 34s
Build and test JVM packages (Linux, Scala 2.12)	10m 14s
Build libxgboost4j.so targeting glibc 2.17 (arch x86_64, runner linux-amd64-cpu)	1m 52s
Build and test JVM packages (windows-latest)	11m 16s
Build and test JVM packages (Linux, Scala 2.13)	5m 4s
Build and test JVM packages (macos-13)	8m 58s
Build docs for JVM packages	4m 33s
Test JVM packages with CUDA (Scala 2.12)	5m 58s
Test JVM packages with CUDA (Scala 2.13)	6m 5s
Deploy JVM packages to S3 (cpu)	6s
Deploy JVM packages to S3 (cpu)	7s
Deploy JVM packages to S3 (gpu)	9s
Deploy JVM packages to S3 (gpu)	7s
	1h 6m 44s

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