Add OpenCV DNN pipeline #769

Job	Run time
PhotonClient Build	38s
Build Examples	5m 43s
Gradle Build	4m 32s
Build Offline Docs	35s
Photonlib - Build Docker - Athena	8m 11s
Photonlib - Build Host - Win64	8m 4s
Photonlib - Build Docker - Raspbian	8m 49s
Photonlib - Build Host - macOS	8m 31s
Photonlib - Build Docker - Aarch64	8m 48s
Photonlib - Build Host - Linux	4m 41s
Build fat JAR - Win64	2m 13s
Build fat JAR - macOS	2m 20s
Build fat JAR - Linux	1m 11s
Build fat JAR - macOSArm	1m 45s
Build fat JAR - LinuxArm32	1m 21s
Build fat JAR - LinuxArm64	1m 7s
Build image - ${{ matrix.image_url }}	0s
release	0s
	1h 8m 29s

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