Extract grouping ID based on configurations

[bryan-lou]

Extract the group ID based on primary grouping option or fallback to a default grouping by invocation

[google-oss-prow[bot]]

Hi @bryan-lou. Thanks for your PR.

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[bryan-lou]

Largely LGTM with a couple of nits, please address those and it's good to be merged!

/hold

Addressed comments

[sultan-duisenbay]

/ok-to-test

[sultan-duisenbay]

/lint

[sultan-duisenbay]

/retest

[bryan-lou]

/retest

[google-oss-prow[bot]]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: bryan-lou, sultan-duisenbay

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Needs approval from an approver in each of these files: - ~~[OWNERS](https://github.com/GoogleCloudPlatform/testgrid/blob/master/OWNERS)~~ [sultan-duisenbay] Approvers can indicate their approval by writing `/approve` in a comment Approvers can cancel approval by writing `/approve cancel` in a comment

[sultan-duisenbay]

/hold cancel