feat(TaskProcessing): add AudioToTextSubtitles TaskType

[edward-ly]

Summary

Adds a core:audio2text:subtitles task type which outputs a subtitles file for speech-to-text tasks instead of plain text transcripts (as is the case for core:audio2text).

TODO

• Ideally, this task should accept both audio and video files as input, but I'm not sure if EShapeType::Audio covers video files in addition to audio files. If not, maybe we should have a separate input shape that does cover both?

Checklist

• Code is properly formatted
• Sign-off message is added to all commits
• Tests (unit, integration, api and/or acceptance) are included
• Screenshots before/after for front-end changes
• Documentation (manuals or wiki) has been updated or is not required
• Backports requested where applicable (ex: critical bugfixes)
• Labels added where applicable (ex: bug/enhancement, 3. to review, feature component)
• Milestone added for target branch/version (ex: 32.x for stable32)

AI (if applicable)

• The content of this PR was partly or fully generated using AI