Validator to provide error message when a job in a stage is triggered by jobs outside of the stage

[VonnyJap]

What happened:

A stage can be initiated by a job outside a stage, allowing a setup job within the stage to be externally triggered. However, a job included in a stage can only be triggered by other jobs within that same stage. Currently, if a user configures a job within the stage to be triggered externally, the validator does not flag an error.

What you expected to happen:

The validator should generate an error when users configure a job within a stage to be triggered by jobs outside of that stage.

How to reproduce it:

When configuring a stage with a job triggered by other jobs outside of the stage, no error is raised for the user until a pipeline execution is initiated.

[github-actions]

Similar issues

1. 51% Allow a stage to declared as an upstream for a job outside of that stage #3026
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3. 30% Dropdown menu does not appear even if the pipeline has build parameters #3082

_{🤖 By issues-similarity-analysis}

[tkyi]

verified in this build: https://beta.cd.screwdriver.cd/pipelines/17908/builds/167161/steps/config-parse-error

18:00:34 $ echo 'Error: backend job has invalid requires: ~acceptance-tests,~promotion-230899,~promotion-1010409. Triggers must be jobs from testing stage.
18:00:34 frontend job has invalid requires: ~acceptance-tests,~promotion-230899,~promotion-1010409. Triggers must be jobs from testing stage.
18:00:34 http-testapp job has invalid requires: ~acceptance-tests,~promotion-230899,~promotion-1010409. Triggers must be jobs from testing stage.
18:00:34 mtls-app job has invalid requires: ~acceptance-tests,~promotion-230899,~promotion-1010409. Triggers must be jobs from testing stage.
18:00:34 role-cert-backend job has invalid requires: ~acceptance-tests,~promotion-230899,~promotion-1010409. Triggers must be jobs from testing stage.
18:00:34 simple-grpc job has invalid requires: ~acceptance-tests,~promotion-230899,~promotion-1010409. Triggers must be jobs from testing stage.
18:00:34 skip-jwt-backend job has invalid requires: ~acceptance-tests,~promotion-230899,~promotion-1010409. Triggers must be jobs from testing stage.
18:00:34 test-app-backend job has invalid requires: ~acceptance-tests,~promotion-230899,~promotion-1010409. Triggers must be jobs from testing stage.
18:00:34 test-app-frontend job has invalid requires: ~acceptance-tests,~promotion-230899,~promotion-1010409. Triggers must be jobs from testing stage.
18:00:34 test-app-trustrole job has invalid requires: ~acceptance-tests,~promotion-230899,~promotion-1010409. Triggers must be jobs from testing stage.
18:00:34 trigger-acceptancetest-monorepo job has invalid requires: ~acceptance-tests,~promotion-230899,~promotion-1010409. Triggers must be jobs from testing stage.'; exit 1
18:00:34 Error: backend job has invalid requires: ~acceptance-tests,~promotion-230899,~promotion-1010409. Triggers must be jobs from testing stage.
18:00:34 frontend job has invalid requires: ~acceptance-tests,~promotion-230899,~promotion-1010409. Triggers must be jobs from testing stage.
18:00:34 http-testapp job has invalid requires: ~acceptance-tests,~promotion-230899,~promotion-1010409. Triggers must be jobs from testing stage.
18:00:34 mtls-app job has invalid requires: ~acceptance-tests,~promotion-230899,~promotion-1010409. Triggers must be jobs from testing stage.
18:00:34 role-cert-backend job has invalid requires: ~acceptance-tests,~promotion-230899,~promotion-1010409. Triggers must be jobs from testing stage.
18:00:34 simple-grpc job has invalid requires: ~acceptance-tests,~promotion-230899,~promotion-1010409. Triggers must be jobs from testing stage.
18:00:34 skip-jwt-backend job has invalid requires: ~acceptance-tests,~promotion-230899,~promotion-1010409. Triggers must be jobs from testing stage.
18:00:34 test-app-backend job has invalid requires: ~acceptance-tests,~promotion-230899,~promotion-1010409. Triggers must be jobs from testing stage.
18:00:34 test-app-frontend job has invalid requires: ~acceptance-tests,~promotion-230899,~promotion-1010409. Triggers must be jobs from testing stage.
18:00:34 test-app-trustrole job has invalid requires: ~acceptance-tests,~promotion-230899,~promotion-1010409. Triggers must be jobs from testing stage.
18:00:34 trigger-acceptancetest-monorepo job has invalid requires: ~acceptance-tests,~promotion-230899,~promotion-1010409. Triggers must be jobs from testing stage.