As a user, I can choose how to assign the Test Runs whenever adding Tests/Test Sets to a Test Execution

As a user, I can choose how to assign the Test Runs whenever adding Tests/Test Sets to a Test Execution.

ACs:

• whenever using Add Tests/Add Test Sets in the context of a Test Execution, the user shall decide how the Test Run assignee will be set (if based on the Test Execution assignee or some other user based field of the Test)
• the user shall not be asked for this, if calling this operation from within a Test Set or Test Plan