Nvidia Jetson ffmpeg + TensorRT support (#6458)

* Non-Jetson changes

Required for later commits:
- Allow base image to be overridden (and don't assume its WORKDIR)
- Ensure python3.9
- Map hwaccel decode presets as strings instead of lists
Not required:
- Fix existing documentation
- Simplify hwaccel scale logic

* Prepare for multi-arch tensorrt build

* Add tensorrt images for Jetson boards

* Add Jetson ffmpeg hwaccel

* Update docs

* Add CODEOWNERS

* CI

* Change default model from yolov7-tiny-416 to yolov7-320

In my experience the tiny models perform markedly worse without being
much faster

* fixup! Update docs

docker/tensorrt/detector/tensorrt_libyolo.sh

@@ -8,7 +8,10 @@ SCRIPT_DIR="/usr/local/src/tensorrt_demos"
 git clone --depth 1 https://github.com/NateMeyer/tensorrt_demos.git -b conditional_download
 
 # Build libyolo
-cd ./tensorrt_demos/plugins && make all
+if [ ! -e /usr/local/cuda ]; then
+    ln -s /usr/local/cuda-* /usr/local/cuda
+fi
+cd ./tensorrt_demos/plugins && make all -j$(nproc)
 cp libyolo_layer.so /usr/local/lib/libyolo_layer.so
 
 # Store yolo scripts for later conversion