Add Motion JPEG extractor support

[osscv]

Summary

• Add an extractor for HTTP multipart Motion JPEG (multipart/x-mixed-replace).
• Support parts with Content-Length and marker-delimited JPEG frames without it.
• Support X-Timestamp, CRLF/LF headers, quoted or inferred boundaries, and partial reads.
• Support raw concatenated .mjpeg and .mjpg streams with a default 25 fps timeline.
• Register MJPEG MIME, file-type, URI, response-header, and default extractor selection.

Motivation

This enables playback of HTTP camera streams such as:

http://61.211.241.239/nphMotionJpeg?Resolution=320x240&Quality=Standard

References

• ISO/IEC 10918-1 (JPEG coding): https://www.iso.org/standard/18902.html
• Apple QuickTime File Format, Video sample data (JPEG and Motion-JPEG background): https://developer.apple.com/documentation/quicktime-file-format/video_sample_data
• MJPEG-over-HTTP reference implementation: https://github.com/valbok/mjpeg-over-http
• FFmpeg MJPEG samples: https://samples.ffmpeg.org/archive/video/mjpeg/
• Live multipart MJPEG sample stream: http://61.211.241.239/nphMotionJpeg?Resolution=320x240&Quality=Standard

The Apple documentation also describes QuickTime-specific Motion-JPEG A/B layouts. Those container-specific variants are outside the scope of this HTTP/raw-stream extractor.

Tests

• ./gradlew :lib-common:testDebugUnitTest --tests androidx.media3.common.FileTypesTest
• ./gradlew :lib-extractor:testDebugUnitTest --tests androidx.media3.extractor.jpeg.MjpegExtractorTest --tests androidx.media3.extractor.DefaultExtractorsFactoryTest