Test file cleanup (pytorch#2040)

* Move test_gpu.cpp to test_gpu1.cpp

* Split test_gpu1.cpp to test_gpu1.cpp, test_gpu2.cpp and test_gpu3.cpp.

Each file should be up to 10K LoC. New tests should be added to
test_gpu3.cpp until it gets 10K LoC.

Author: naoyam

test/cpp/jit/CMakeLists.txt

@@ -99,7 +99,9 @@ if(USE_CUDA)
   list(APPEND JIT_TEST_SRCS ${TORCH_SRC_DIR}/csrc/jit/codegen/cuda/python_frontend/test/test_nvfuser_fusion_definition.cpp)
   list(APPEND JIT_TEST_SRCS ${TORCH_SRC_DIR}/csrc/jit/codegen/cuda/python_frontend/test/test_nvfuser_fusion_cache.cpp)
   list(APPEND JIT_TEST_SRCS ${TORCH_SRC_DIR}/csrc/jit/codegen/cuda/python_frontend/test/test_nvfuser_fusion_record.cpp)
-  list(APPEND JIT_TEST_SRCS ${TORCH_SRC_DIR}/csrc/jit/codegen/cuda/test/test_gpu.cpp)
+  list(APPEND JIT_TEST_SRCS ${TORCH_SRC_DIR}/csrc/jit/codegen/cuda/test/test_gpu1.cpp)
+  list(APPEND JIT_TEST_SRCS ${TORCH_SRC_DIR}/csrc/jit/codegen/cuda/test/test_gpu2.cpp)
+  list(APPEND JIT_TEST_SRCS ${TORCH_SRC_DIR}/csrc/jit/codegen/cuda/test/test_gpu3.cpp)
   list(APPEND JIT_TEST_SRCS ${TORCH_SRC_DIR}/csrc/jit/codegen/cuda/test/test_gpu_tensor_factories.cpp)
   list(APPEND JIT_TEST_SRCS ${TORCH_SRC_DIR}/csrc/jit/codegen/cuda/test/test_gpu_fused_reduction.cpp)
   list(APPEND JIT_TEST_SRCS ${TORCH_SRC_DIR}/csrc/jit/codegen/cuda/test/test_gpu_shift.cpp)