Add ElevenLabs as a Provider for Speech to Text

[dkotter]

Description of the Change

At the moment we only have a single Provider for the Audio Transcripts Generation Feature (Speech to Text), and that is OpenAI. This PR brings in ElevenLabs as a Provider there.

No functional changes have been made to this Feature, it just now supports another Provider. One benefit of ElevenLabs is they have a free tier that supports 2 hours 30 minutes of Speech to Text each month, so if you have limited transcription needs, you may be able to use ElevenLabs and not have any cost.

They also seem to support multiple languages better than OpenAI, so that could also be a good reason to use them.

Note: probably worth a followup to add ElevenLabs as a Text to Speech Provider once this is merged in, as that will be pretty easy at that point.

Closes #986

How to test the Change

1. If you don't have an ElevenLabs account, you'll need to sign up for one (it is free)
2. In your account, create an API key and ensure you have the Speech to Text endpoint enabled and Read access to the Models information (which we use to validate the connection)
3. Turn on Audio Transcripts Generation, select ElevenLabs and enter your API key
4. Save settings and ensure no error happens
5. If desired, change the model it uses (there are only two available right now)
6. Upload a new audio file and ensure the transcription is generated and stored in the Description field
7. In an existing audio file, ensure you can generate a transcription both from the media modal and the single edit view

Changelog Entry

Added - ElevenLabs as a new Provider for the Audio Transcripts Generation Feature (Speech to Text)
Changed - Moved some methods from the OpenAI Speech to Text Provider class to the Audio Transcripts Generation Feature class, to avoid code duplication. If relying on those methods, please update your code

Credits

Props @dkotter, @jeffpaul

Checklist:

• I agree to follow this project's Code of Conduct.
• I have updated the documentation accordingly.
• I have added Critical Flows, Test Cases, and/or End-to-End Tests to cover my change.
• All new and existing tests pass.

[iamdharmesh]

Code looks great and tests well. Thanks for adding this @dkotter