"mjpg" or "jpeg" #EXT-X-FRAME-STREAM-INF variant support

[robwalch]

Add support for EXT-X-FRAME-STREAM-INF variants with image codecs. Because image codecs are generally not supported by MSE, these variants will require separate treatment. Variants that are not supported by MSE will still be filtered out from being used as levels and streaming to a SourceBuffer. What we can do is offer a method to request image data based on a time or segment reference and return that asynchronously or via event.

Originally posted by @nvkhoi112358 in #5392 :

Do you have plan to support thumbnail/trickplay in mjpg format?
https://developer.apple.com/documentation/http-live-streaming/hls-authoring-specification-for-apple-devices-appendixes#I-frame-image-sequences

I-frame image sequences using the mjpg codec have been added to support some third-party devices. The sequences should be low bandwidth and require minimal processing. Players should prefer video I-frame variants over image sequences.

[nvkhoi112358]

FYI, a sample stream https://devstreaming-cdn.apple.com/videos/streaming/examples/adv_dv_atmos/main.m3u8

which contains thumbnail MJPG track

#EXT-X-I-FRAME-STREAM-INF:AVERAGE-BANDWIDTH=177512,BANDWIDTH=296000,VIDEO-RANGE=SDR,CODECS="mjpg",RESOLUTION=400x226,URI="Job8208634a-0add-4223-9782-600c14a70339-139240443_Merged_Main_motionJpegTrickPlay_VT_HLS211_tier1/iframe_index.m3u8"