Created test case for pytorch frontend

hpvm/test/CMakeLists.txt

hpvm/test/dnn_benchmarks/pytorch/CMakeLists.txt

hpvm/test/dnn_benchmarks/pytorch/alexnet2_cifar10.test

hpvm/test/dnn_benchmarks/pytorch/alexnet_cifar10.test

hpvm/test/dnn_benchmarks/pytorch/alexnet_imagenet.test

hpvm/test/dnn_benchmarks/pytorch/lenet_mnist.test

hpvm/test/dnn_benchmarks/pytorch/lit.cfg.py

hpvm/test/dnn_benchmarks/pytorch/mobilenet_cifar10.test

hpvm/test/dnn_benchmarks/pytorch/resnet18_cifar10.test

hpvm/test/dnn_benchmarks/pytorch/resnet50_imagenet.test

hpvm/test/dnn_benchmarks/pytorch/test_frontend.py

hpvm/test/dnn_benchmarks/pytorch/vgg16_cifar10.test

hpvm/test/dnn_benchmarks/pytorch/vgg16_cifar100.test

hpvm/test/dnn_benchmarks/pytorch/vgg16_imagenet.test