fix: check manifests kinds when running a Job

[boonware]

Issue

spinnaker/spinnaker#6769

Description

• Allow a manifest file to contain more than one embedded manifest when running a Job. This supports use cases such as a Job manifest bundled with a ConfigMap manifest in the same file. Strictly speaking, it is a manifest file containing more than one Job definition that is the problem. This is solved by checking the kind of each manifest in the file, and only throwing an exception if more than one Job kind is found.
• If necessary, further filtering could be added to check for other executable kinds, see https://kubernetes.io/docs/reference/kubernetes-api/workload-resources/

[boonware]

@dbyron-sf Could I get a workflow approval, please?

[dbyron-sf]

No need to tag me on PRs. I see them fly by.

I'm not sure I agree that this is a fix though. Seems more like a feature/change in behavior, and one that could break folks who depend on this validation. I think I'd prefer that additional work go into filtering so it's possible to leave run job stages alone and deploy the additional manifests (presumably without the job) in a deploy manifest stage.