Remove usage of issues.issue_type column

What does this MR do and why?

Another MR as part of the effor to remove the issues.issue_type column as described in Replace use of `issues.issue_type` column with ... (#338005 - closed)

Only some changes are behind a feature flag in places where I thought it might be safer since we could affect performance

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.

Related to #338005 (closed)