Create EngineHolder for serializing and running TRT Engines with PyTorch
Test Plan:
**python tests**
`buck test mode/opt -c python.package_style=inplace -c fbcode.platform=platform009 -c fbcode.enable_gpu_sections=true -j 20 deeplearning/trt/EngineHolder:engine_holder_test`
**python tests to generate test models** (this outputs the jit model files for use with cpp tests)
`buck run mode/opt -c python.package_style=inplace -c fbcode.platform=platform009 -c fbcode.enable_gpu_sections=true -j 20 deeplearning/trt/EngineHolder:engine_holder_generate_test_models`
**cpp tests**
`buck test mode/opt -c python.package_style=inplace -c fbcode.platform=platform009 -c fbcode.enable_gpu_sections=true -j 20 deeplearning/trt/EngineHolder:engine_holder_test_cpp`
**run service locally**
*build service*
`buck build mode/opt-split-dwarf -c fbcode.platform=platform009 -c fbcode.enable_gpu_sections=true -j 20 smart/inference_platform_sp/predictor_gpu:service`
*run service*
`buck-out/gen/smart/inference_platform_sp/predictor_gpu/service --model_dir="/home/jackmontgomery" --model_id=123_0 --pytorch_predictor_use_cuda`
*build requester*
`buck build mode/opt -c python.package_style=inplace -c fbcode.platform=platform009 -c fbcode.enable_gpu_sections=true -j 20 glow/fb/test:invoke_cv_pt_predictor`
*run requester*
`buck-out/gen/glow/fb/test/invoke_cv_pt_predictor.par --model_id=123_0 --port=33131 --host="2401:db00:eef0:1100:3560:0:1c02:2115" --num_parallel_requesters=1`
Reviewed By: 842974287
Differential Revision: D28581591
fbshipit-source-id: 7738b05543c2c840ee6b8f0d4818f21dc7f61b19
