Add Sort by Last Updated to Issue/MR Sort Options in Global Search

Originally Pointed out here. #25687

Users should have the ability to sort results lists for Issues and MRs by Last Updated.

This can help with larger and older Instances where users are dealing with duplicates and similar issues and MRs.

On the issues page, Last updated is the second most used Feature.

Release notes

On the GitLab search result page, we have a dropdown list where users can choose to sort the results by certain criteria. In GitLab 13.9, we added another option in the dropdown list where users can sort the issues and MRs results by their last updated time.