Refactor Dokcerfile.cpp and documentation

[namannandan]

Description

Address follow up review comments on: #2976

Type of change

• Bug fix (non-breaking change which fixes an issue)

Feature/Issue validation/testing

• Manual test

$ ./build_image.sh -g -bt dev -cv cu118 -cpp

$ docker images
REPOSITORY           TAG                               IMAGE ID       CREATED          SIZE
pytorch/torchserve   cpp-dev-gpu                       01f3de83e243   38 minutes ago   10.4GB

$ docker run --gpus all -it 01f3de83e243 /bin/bash

root@ddffb9dd9111:/serve# python ts_scripts/install_dependencies.py --environment=dev --cuda=cu118 --cpp

root@ddffb9dd9111:/serve# gcc --version
gcc (Ubuntu 9.4.0-1ubuntu1~20.04.2) 9.4.0
Copyright (C) 2019 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

root@ddffb9dd9111:/serve# cmake --version
cmake version 3.26.4

CMake suite maintained and supported by Kitware (kitware.com/cmake).

root@ddffb9dd9111:/serve# cd cpp
root@ddffb9dd9111:/serve/cpp# ./build.sh
root@ddffb9dd9111:/serve# cd ..

root@ddffb9dd9111:/serve# export LD_LIBRARY_PATH=`python -c "import torch;from pathlib import Path;p=Path(torch.__file__);print(f\"{(p.parent / 'lib').as_posix()}:{(p.parents[1] / 'nvidia/nccl/lib').as_posix()}\")"`:$LD_LIBRARY_PATH
root@ddffb9dd9111:/serve# mkdir model_store
root@ddffb9dd9111:/serve# torchserve --ncs --start --model-store ./model_store --models mnist=/serve/cpp/_build/test/resources/examples/mnist/mnist_handler/
root@ddffb9dd9111:/serve# curl http://127.0.0.1:8080/predictions/mnist -T /serve/cpp/_build/test/resources/examples/mnist/0_png.pt --output out.pt
root@ddffb9dd9111:/serve# python -c "import torch; print(torch.load('out.pt'))"
tensor(0, device='cuda:0')