Tests

port tests for rgb_to_grayscale functional and transforms #1464

Job	Run time
unittests-extended / linux-job	57s
onnx / linux-job	56s
unittests-linux (3.10, linux.12xlarge, cpu) / linux-job	46s
unittests-linux (3.11, linux.12xlarge, cpu) / linux-job	44s
unittests-linux (3.8, linux.12xlarge, cpu) / linux-job	35s
unittests-linux (3.8, linux.g5.4xlarge.nvidia.gpu, cuda, 11.8) / linux-job	55s
unittests-linux (3.9, linux.12xlarge, cpu) / linux-job	32s
unittests-macos (3.11, macos-12) / macos-job	1m 51s
unittests-macos (3.10, macos-12) / macos-job	1m 38s
unittests-macos (3.8, macos-12) / macos-job	1m 45s
unittests-macos (3.8, macos-m1-12) / macos-job	1m 29s
unittests-macos (3.9, macos-12) / macos-job	1m 26s
unittests-windows (3.10, windows.4xlarge, cpu) / windows-job	3m 15s
unittests-windows (3.11, windows.4xlarge, cpu) / windows-job	3m 21s
unittests-windows (3.8, windows.4xlarge, cpu) / windows-job	3m 2s
unittests-windows (3.8, windows.g5.4xlarge.nvidia.gpu, cuda, 11.8) / windows-job	42s
unittests-windows (3.9, windows.4xlarge, cpu) / windows-job	3m 11s
	27m 5s

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