cherrypick: do not abort on first failure

[valen-mascarenhas14]

Fix for #544
This change fixes the behavior in the cherrypicker plugin where processing would stop after the first cherry-pick failure, even if additional valid targets were requested in the same comment.
The logic is updated to continue processing remaining branches while aggregating and reporting all errors at the end.

Key change

var errs []error

for _, targetBranch := range sets.List(sets.KeySet(commands)) {
    if err := s.handle(...); err != nil {
        errs = append(errs, err)
        continue 
    }
}

if len(errs) > 0 {
    return log, utilerrors.NewAggregate(errs)
}

This ensures that:

• Successful cherry-picks are not skipped due to unrelated failures
• Failures are still properly surfaced to the user

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[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: valen-mascarenhas14
Once this PR has been reviewed and has the lgtm label, please assign matthyx for approval. For more information see the Code Review Process.

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• cmd/external-plugins/cherrypicker/OWNERS

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[k8s-ci-robot]

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[k8s-ci-robot]

Hi @valen-mascarenhas14. Thanks for your PR.

I'm waiting for a github.com 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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[matthyx]

/ok-to-test

[matthyx]

/lgtm