Fix AI Search vector store and refactor audience parameter

[KennyZhang1]

Description

This PR improves support for manage identities by clarifying and updating the "audience" parameter in the config file.

Related Issues

N/A

Proposed Changes

Since the parameter "cognitive_services_endpoint" is unclear for certain users, specifically those not using a cognitive services resource, the codebase has been refactored to use a more generic "audience" parameter in place of this configuration.

Checklist

• [x] I have tested these changes locally.
• [x] I have reviewed the code changes.
• [ ] I have updated the documentation (if necessary).
• [ ] I have added appropriate unit tests (if applicable).

Additional Notes

N/A

[AlonsoGuevara]

Hey Kenny, is this intended to be kept as a Draft?

[jgbradley1]

While reviewing this PR, I found some missing documentation for the vector_store config settings. Will go ahead and add the missing documentation to this PR since this touches on the AI Search vector store audience parameter as well.