Add TensorRT Python interface and CLI

[zhiqwang]

Add the TensorRT Python CLI for yolort:

python tools/detect.py --weights yolov5.engine
                       --source ./test/assets/bus.jpg
                       --img_size 320 320
                       --conf_thres 0.35

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[codecov]

Codecov Report

Merging #251 (f91f899) into main (5dd25c3) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main     #251   +/-   ##
=======================================
  Coverage   93.62%   93.62%           
=======================================
  Files          11       11           
  Lines         675      675           
=======================================
  Hits          632      632           
  Misses         43       43           

Flag	Coverage Δ
unittests	93.62% <ø> (ø)

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