STT: Endpoint for audio files

[nishika26]

Describe the current behavior
Currently, there is no endpoint to get and list audio files for STT evaluations. This limits our ability to effectively manage and utilize audio data for testing.

Describe the enhancement you'd like

• Create an endpoint to retrieve a list of audio files.
• Implement functionality to fetch specific audio files.
• Include signed url of the file as well in the response body of both these endpoint
• add "include signed url" as a boolean flag in these endpoints
• Ensure it integrates seamlessly with existing STT evaluation processes.