Support NVDEC in Streamer

[mthrok]

This issue is a tracker for enabling Nvidia NVDEC based decoding ("cuvid" codec variants) within Streamer API.

It will require a version of ffmpeg with NVDEC support, which is not distributable, so users will have to compile ffmpeg by themselves. It's outlined here.

Minimum

• Support specifying decoder and its options #2327
  Allows to specify "h264_cuvid" as decoder, with CUDA-based resizing "resize=widthxheight" option.
• Support NV12 format in video decoding #2330
  Allows to convert decoded frame in NV12 format into Tensor format. NV12 is a variant of YUV format that NVDEC produces.
• Add HW acceleration support to Streamer #2331
  Allows to keep the decoded frame in CUDA memory.

Stretch

• Add support for P010 format
• Add support for P016 format
• Add YUV420P format support to Streamer API #2334
• Allow specifying GPU when multiple GPUs are available