Add test cases for work items title and milestone

What does this MR do and why?

Add rpecs for work items. Check if title is changed correctly.
Check if milestone is searched, changed and removed for a work item.
Select label title instead of body as body is failing sometimes.

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 #392476 (closed)