Allow separate Auth config for Catalog definitions

[vordimous]

Describe the desired outcome from the user's perspective
As a system admin, I need to separate the user credentials for my schema registry Catalog and my data layer.

Acceptance criteria

• Provide config options to indicate Authentication credentials that only apply to the Catalog requests

Additional context
Docs for adding Schema Registry API key for Confluent Cloud
Docs for adding Schema Registry auth for Redpanda
Docs for adding Schema Registry auth for Karapace