enhance highgui module with hardware acceleration

[nihui]

cv::imread / cv::imdecode

• jpeg on milkv-duo
• jpeg on yuzuki-lizard
• jpeg on tinyvision

cv::imwrite / cv::imencode

• jpeg on milkv-duo
• jpeg on yuzuki-lizard
• jpeg on tinyvision
• jpeg on luckfox-pico

cv::VideoCapture

• v4l camera on luckfox-pico
• v4l camera on tinyvision
• cvi camera on milkv-duo

[nihui]

1920x1080 jpg encoding on raspberry pi

• software encoder: opencv + libjpeg-turbo
• hardware encoder: v4l2-mem
• write to /dev/null for eliminating i/o time

	soc	sw(ms)	sw-cpu-usage(%)	hw(ms)	hw-cpu-usage(%)
rpib+	BCM2835	766.26	97.2	41.36	41.8
rpi2	BCM2836	185.87	100	29.92	22.4
rpi3b+	BCM2837B0	65.02	100	22.69	23.8
rpi4b	BCM2711	31.81	100	14.91	16.9
rpi5b	BCM2712	15.83	100	n/a	n/a