Add endpoints to paginate deploy keys by type

What does this MR do and why?

This will give the frontend the ability to fetch a specific set of deploy keys at at time, reducing page load times and DB query time.

Query Plans

• enabled_keys (internal link)
• available_project_keys (internal link)
• available_public_keys (internal link)

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

For #407604 (closed)