chore: Update test READMEs to reflect correct information on testing workflows

[DharmitD]

Description of your changes:

• Remove obsolete information related to Prow tests, and gcloud dependency, since we've moved to GH Action Workflows/ Kind.
• Add details related to the newly added GHA workflows and how to replicate them locally/manually using Kind clusters.

Resolves #11061

Checklist:

• You have signed off your commits
• The title for your pull request (PR) should follow our title convention. Learn more about the pull request title convention used in this repository.

[rimolive]

/lgtm

[VaniHaripriya]

/lgtm

[hbelmiro]

Nice job @DharmitD. I left a few suggestions.

Also, can you please:

• Update/remove:
  • https://github.com/kubeflow/pipelines/blob/master/samples/test/README.md
  • https://github.com/kubeflow/pipelines/blob/master/sdk/python/test_data/README.md (I'm not sure that one is outdated)
• Link Remove obsolete README files after migrating tests to GitHub Actions #11061 to this PR

[DharmitD]

Update/remove:

• https://github.com/kubeflow/pipelines/blob/master/samples/test/README.md
• https://github.com/kubeflow/pipelines/blob/master/sdk/python/test_data/README.md (I'm not sure that one is outdated)

Thanks! I updated both these READMEs to point to the right files.

[hbelmiro]

/lgtm

[hbelmiro]

@chensun @HumairAK can you please approve if that makes sense to you?

[chensun]

/lgtm
/approve

Thanks!

[google-oss-prow]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: chensun, hbelmiro

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