test(v2): presubmit unit tests of v2

[capri-xiyue]

Description of your changes:
fixed #5685
presubmit unit tests of v2
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.

[capri-xiyue]

@Bobgy Looks like I need to add this presubmit tests into some prow config. Do you know where the prow config is?

GoogleCloudPlatform/oss-test-infra#890 submitted

[Bobgy]

Thank you!
Shall we call this presubmit-go-v2 test to be more specific?

[capri-xiyue]

Thank you!
Shall we call this presubmit-go-v2 test to be more specific?

How about presubmit-go-v2-task-handler-test?

[Bobgy]

Thank you!
Shall we call this presubmit-go-v2 test to be more specific?

How about presubmit-go-v2-task-handler-test?

We'll keep building KFP v2 go code in this folder, so it won't be task-handler specific by then.

[capri-xiyue]

Thank you!
Shall we call this presubmit-go-v2 test to be more specific?

How about presubmit-go-v2-task-handler-test?

We'll keep building KFP v2 go code in this folder, so it won't be task-handler specific by then.

How about presubmit-go-v2-backend-test?

[capri-xiyue]

/test kubeflow-pipelines-samples-v2

[Bobgy]

/lgtm
/approve
/retest

[google-oss-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: Bobgy

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[Bobgy]

Thank you!

Note, adding a test should start with test PR type