Pull label and language from embedded captions to populate in Avalon caption

[elynema]

Description

When pulling caption tracks from the .mp4 container (see #5702 for initial work), the caption label/name is currently be auto-generated based on the filename.

It would be great to pull any label and language from the text track (if they exist) to populate those fields in Avalon.

Done Looks Like

• Investigate location in file container metadata for label and language values associated with timed text tracks
• find an example of a media file with these qualities for testing
• implement retrieval of label and language metadata for adding to supplemental file metadata fields