Integrate yocto-test-suite/video_dl_update

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Commit: seco-ne/tools/yocto-test-suite@5bed21fd

video-tests: add config files for iMX8MM boards

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Commit: seco-ne/tools/yocto-test-suite@b829c279

video-tests: update download routine

Updated the part of script that downloads the test videos from the
provided URLs. The new version allows to set a custom name for output
files. It is useful if filenames are the same but files are pulled
from different sources. This renaming can be achieved by
adding a custom name (separated by one or more spaces) after the URL.
For example:

TEST_VIDEO_URLS="\
https://test-videos.co.uk/vids/bigbuckbunny/mp4/h264/1080/Big_Buck_Bunny_1080_10s_5MB.mp4   Big_Buck_Bunny_1080_10s_5MB_h264.mp4
https://test-videos.co.uk/vids/bigbuckbunny/mp4/h265/1080/Big_Buck_Bunny_1080_10s_5MB.mp4   Big_Buck_Bunny_1080_10s_5MB_h265.mp4
"

The commit also updates names of several variables to more accurately
reflect their meaning.