[CUDA] remove src/treelearner/kernels #9497

Job	Run time
r-package (ubuntu-latest, gcc, R 4.3, cmake)	8m 52s
r-package (ubuntu-latest, clang, R 4.3, cmake)	9m 17s
r-package (macos-13, gcc, R 4.3, cmake)	10m 15s
r-package (clang16, R-devel)	12m 13s
r-package (macos-13, clang, R 4.3, cmake)	9m 18s
r-sanitizers (ubuntu-latest, R-devel, gcc ASAN/UBSAN)	15m 32s
r-package (clang17, R-devel)	12m 12s
r-package (windows-latest, MINGW, R 3.6, cmake)	12m 19s
r-sanitizers (ubuntu-latest, R-devel, clang ASAN/UBSAN)	29m 20s
r-package (windows-latest, MINGW, R 4.3, cmake)	16m 5s
r-package (clang18, R-devel)	12m 16s
r-package (clang19, R-devel)	12m 19s
r-package (windows-2019, MSVC, R 3.6, cmake)	23m 40s
r-package (gcc14, R-devel)	11m 2s
r-package (windows-2022, MSVC, R 4.3, cmake)	24m 49s
r-package (intel, R-devel)	11m 46s
r-package (windows-latest, MINGW, R 3.6, cran)	13m 4s
r-package (rchk, R-devel)	12m 40s
r-package (windows-latest, MINGW, R 4.3, cran)	14m 4s
r-package (ubuntu-latest, gcc, R 4.3, cran)	10m 59s
r-package (macos-13, clang, R 4.3, cran)	9m 49s
r-package (macos-14, clang, R 4.3, cran)	6m 36s
all-r-package-jobs-successful	2s
	4h 58m 29s

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