Invite user to slack when FF triggered e2e tests fail

What does this MR do?

Invite a user to qa-staging or qa-production channels when an e2e pipeline triggered due to their toggling of a FF fails.

Related to: https://gitlab.com/gitlab-org/quality/team-tasks/-/issues/1097

Requires: gitlab-org/gitlab-build-images!456 (merged)

Check-list

• Verify the change in all affected pipelines.