Add sample tests for all core samples

[gaoning777]

No description provided.

[jessiezcc]

@gaoning777, pls assign to whoever is helping on this project

[gaoning777]

This will depend on some test infra improvement that jiaxiao is working on.

[gaoning777]

adding some core sample tests: #2030

[gaoning777]

List of not-tested core samples:
https://github.com/kubeflow/pipelines/tree/master/samples/core/ai-platform Done
https://github.com/kubeflow/pipelines/tree/master/samples/core/artifact_location Done
https://github.com/kubeflow/pipelines/tree/master/samples/core/component_build Done
https://github.com/kubeflow/pipelines/tree/master/samples/core/execution_order Done
https://github.com/kubeflow/pipelines/tree/master/samples/core/imagepullsecrets Done
https://github.com/kubeflow/pipelines/tree/master/samples/core/kubeflow_tf_serving Done
https://github.com/kubeflow/pipelines/tree/master/samples/core/multiple_outputs Done
https://github.com/kubeflow/pipelines/tree/master/samples/core/preemptible_tpu_gpu Done
https://github.com/kubeflow/pipelines/tree/master/samples/core/resource_ops Done
https://github.com/kubeflow/pipelines/tree/master/samples/core/retry Done
https://github.com/kubeflow/pipelines/tree/master/samples/core/sidecar Done
https://github.com/kubeflow/pipelines/tree/master/samples/core/tfx-oss Done
https://github.com/kubeflow/pipelines/tree/master/samples/core/volume_snapshot_ops Done

[gaoning777]

adding multiple output sample test: #2109

[numerology]

Suggestion: Maybe not cover retry sample for now due to its non-deterministic behavior.

[gaoning777]

Thanks Jiaxiao for the efforts.

[gaoning777]

sidecar test: #2106

[gaoning777]

component build sample: #2109

[gaoning777]

There are some sample tests that require extra work:
Category 1) non-determinism. Samples such as retry is non-deterministic. There is no sample test infra support for such non-deterministic behaviors. We will run the DSL compiler against it without running the pipeline. Since retry is part of the argo support, this is sufficient for now to only test the DSL compilation.
Category 2) platform support. Samples such as preemptible_tpu_gpu requires more platform configurations, which is not supported by the sample test infra. This support is quite complex and deprioritized for now.

[gaoning777]

retry: #2141

[gaoning777]

artifact location: #2142

[gaoning777]

Updated the assignment.

[gaoning777]

preemptible vm&volume snapshot: #2149

[gaoning777]

@Ark-kun any progress on the multiple output test?

[gaoning777]

resource_ops sample test: #2274