Add speech-to-text pipeline

[eliteprox]

What does this pull request do? Explain your changes. (required)

Adds the new /speech-to-text pipeline to go-livepeer, supporting the openai/whisper-large-v3 model.

File formats supported are mp3, m4a, mp4, webm, wav and flac

This change requires livepeer/ai-worker#103

Specific updates (required)

• Refactors handleAIRequest and processAIRequest to support new response types like TextResponse
• Adds /speech-to-text endpoint to ai_mediaserver.go
• Pricing fixed to one pixel per millisecond

How did you test each of these updates (required)

• Tested with rich vocal audio up to 4 hours long. Regression tested other pipelines to ensure refactoring cause any issues.
• Tested with all supported file formats and unsupported ones

curl request example:

curl --request POST   --url http://dev.eliteencoder.net:8937/speech-to-text --header 'Content-Type: multipart/form-data'   --form '[email protected]'   --form 'model_id=openai/whisper-large-v3'   --form seed=123

Does this pull request close any open issues?

LIV-429
LIV-289

Checklist:

• Read the contribution guide
• make runs successfully
• All tests in ./test.sh pass
• README and other documentation updated
• Pending changelog updated

[eliteprox]

Added error handlers to respond with "400 bad request" when duration cannot be calculated due to unsupported file format or file corruption. This prevents invalid jobs from being sent to the network.