add support for nvenc and accel_assist #2251

Job	Run time
code formatting check	13s
cppcheck	3m 55s
min features with gcc	2m 28s
min features with g++	2m 29s
min features with clang	1m 53s
max features with gcc	3m 8s
max features with g++	2m 20s
max features with clang	3m 31s
max features with clang and AddressSanitized	2m 23s
max features with gcc and DEBUG	2m 36s
max features with gcc for 32-bit arch (legacy OS)	1m 34s
max features with g++ for 32-bit arch (legacy OS)	1m 31s
max features with clang for 32-bit arch (legacy OS)	2m 38s
	30m 39s

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