Group Import history - Default sort by Date descending

What does this MR do and why?

This MR introduces sort param for bulk_imports API and makes order as descending by default

How to set up and validate locally

1. Initiated couple gitlab migrations using /group/new -> Import -> GitLab migration
2. Observe /api/v4/bulk_imports presenting imports in correct way

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 #354677 (closed)