fix(backend): Use an Argo Workflow exit lifecycle hook for exit handlers

[mprahl]

Description of your changes:

As described in #10917, exit handlers were implemented as dependent tasks that always ran within an Argo Workflow. The issue is that this caused the pipeline to have a succeeded status regardless of if the tasks within the exit handlers all succeeded.

This commit changes exit handlers to be exit lifecycle hooks on an Argo Workflow so that the overall pipeline status is not impacted.

Resolves:
#11405

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[google-oss-prow]

Hi @mprahl. Thanks for your PR.

I'm waiting for a kubeflow member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

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[hbelmiro]

/lgtm
/ok-to-test

[mprahl]

@hbelmiro I rebased the PR and added an additional Argo compiler unit test.

[hbelmiro]

/lgtm

[mprahl]

@hbelmiro and @HumairAK I just rebased this PR.

[hbelmiro]

/lgtm

[HumairAK]

wonderful thanks @mprahl !

I also verified the following scenarios:

• parent pipeline has failure inside an exit task handler
• nested pipelines has failure inside an exit task handler

and works as intended, great work!

/lgtm
/approve

[google-oss-prow]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: HumairAK

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