feat(sample): Add markdown visualization example for v1 and v2 compatible

[zijianjoy]

Description of your changes:
Partial #5932

Ability to run same pipeline for v1 and v2 compatible, it will generate Markdown for UI visualization.

Command to initialize test:

python3 -m samples.core.visualization.markdown_test

Checklist:

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

[Bobgy]

Thank you for building an example for markdown!

[Bobgy]

/lgtm

[Bobgy]

/retest

[Bobgy]

Note, the title has to be feat(scope): title. Do not omit the : and the space.

[Bobgy]

/lgtm
/approve
Thank you for adding the two samples!

[google-oss-robot]

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This pull-request has been approved by: Bobgy

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[zijianjoy]

Note, the title has to be feat(scope): title. Do not omit the : and the space.

Thank you Yuan @Bobgy for the reminder! I should remember to add the : and space to title.

On the related note, I wonder if it helps if we align the approach of title naming with issue creation? On Issue creation, we add labels areas/frontend, areas/samples. It will be shown on the PR title when we visit https://github.com/kubeflow/pipelines/pulls, and we can filter by label to find issues under certain area as well.