[GPU] Add option for no gpu.block_dim in GPUDistributeScfFor #25136

Job	Run time
setup / setup	11s
build_test_all_macos_x86_64	0s
build_test_all_bazel	4m 38s
build_test_all_arm64	0s
build_test_all_macos_arm64	0s
build_test_runtime	7m 22s
build_test_runtime_windows	17m 55s
asan	13m 13s
build_test_runtime_arm64	3m 1s
gcc	5m 32s
python_release_packages	17m 19s
small_runtime	3m 50s
tsan	17m 40s
byo_llvm	7m 1s
debug	17m 26s
tracing	1m 49s
build_all / build_all	8m 46s
test_nvidia_gpu	8m 48s
cross_compile_and_test (linux, riscv_64, lp64d, gcr.io/iree-oss/riscv@sha256:62e87bad3405d691ddba...	3m 38s
cross_compile_and_test (linux, riscv_32, ilp32d, gcr.io/iree-oss/riscv@sha256:62e87bad3405d691ddb...	4m 6s
build_e2e_test_artifacts	0s
build_benchmark_tools	0s
cross_compile_and_test (generic, riscv_32, ilp32, gcr.io/iree-oss/riscv@sha256:62e87bad3405d691dd...	2m 12s
test_nvidia_a100	0s
cross_compile_and_test (emscripten, wasm32, wasm32, gcr.io/iree-oss/emscripten@sha256:2dd4c52f1bb...	4m 39s
build_and_test_android / cross_compile	2m 25s
test_benchmark_suites	0s
compilation_benchmarks	0s
execution_benchmarks	0s
process_benchmark_results	0s
build_and_test_android / test_on_${{ matrix.target.device-name }}	0s
summary	6s
	2h 31m 37s

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