Frontend: Add toast notification

Summary

Related to work and testing done in #367547 (closed), when the trigger job is retried in the pipeline graph, the old downstream pipeline disappears while the new one is still being created.

Proposal

The proposal is to add a toast notification here informing users that:

Downstream pipeline could be disappeared while the new one is being created

Additional details

Some relevant technical details, if applicable, such as:

• Does this need a feature flag?
• Is there an example response showing the data structure that should be returned (new endpoints only)?
• What permissions should be used?
• Is this EE or CE?
  • EE
  • CE
• Additional comments:

Implementation Table

Group	Issue Link
frontend	#367547 (closed)
frontend	👈 You are here

Links/References