Solicit feedback for Classification Subtype to expand coverage

Objective

Identify candidate subtypes to reduce undefined subtype rate.

Subtypes added

With !107891 (merged)

• ~"bug::functional": Functional defects resulting from feature changes
• ~"bug::ux": Unexpected and unintended behavior that is detrimental to the user experience.
• ~"maintenance::performance": Non-defect performance improvements such as load time for a specific page or component, or run time for a specific process.
• maintenancescalability`: Modification to improve the scalability of GitLab that is not a user facing change or performance improvement. For example changing a column from INT to BIGINT.

Subtype gaps

• maintenance::data-cleanup - Merge requests that add migrations to removing invalid records or clean up database records => gitlab-org/gitlab!80253 (comment 1069213829)

cc: @meks