Add testing for MilestonePrompt()

Created by: maxice8

Description

• feat(pkg/prompt): add Select() to select a single option
• refactor(commands/cmdutils): use the new prompt.Select()
• test(command/cmdutils): add tests for MilestonePrompt()

How Has This Been Tested?

Create Merge Request with path where cmdutils.MilestonePrompt() is invoked