Refactor resource op sample for sample test coverage

[numerology]

Currently resource op sample illustrates the usage of mounting credential through resource op, which is not a good practice because password might not be masked in the KFP UI.

This PR changes that to an example showing how to run a container by a resource op.

Also sample test coverage is added.

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This change is 

[Ark-kun]

"Error from server (Forbidden): error when creating \"/tmp/manifest.yaml\": configmaps is forbidden: User \"system:serviceaccount:kubeflow:pipeline-runner\" cannot create resource \"configmaps\" in API group \"\" in the namespace \"default\"\ngithub.com/argoproj/argo/errors.New\n\t/go/src/github.com/argoproj/argo/errors/errors.go:49\ngithub.com/argoproj/argo/workflow/executor.

[Ark-kun]

/lgtm

[Ark-kun]

/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: Ark-kun

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