Clean up tofa* db columns

What does this MR do and why?

• This was a codename used for Vertex AI before we were ready to publicly announce this integration
• Many of these columns contained non-sensitive data but were being used to obscure code. Those values can now safely be hard-coded. Sensitive values can remain as settings but should be renamed for clarity
• The remaining setting with tofa in the name is tofa_url. That should receive further refactoring because the way we are handling it today is weird (there is a hard-coded URL and then we use gsub to change it for other models) so I will handle that separately.
• Partially addresses https://gitlab.com/gitlab-org/gitlab/-/issues/408829

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