Introduce stubTransition helper

What does this MR do?

@vue/test-utils 1.x will not autostub transitions anymore. Instead their docs recommend different approaches. One of them is picked and implemented in stub_transition helper

Part of &4255 (closed) effort

#240756 (closed)

Screenshots (strongly suggested)

N/A

Does this MR meet the acceptance criteria?

Conformity

• Code review guidelines
• Merge request performance guidelines
• Style guides