Per-feature Flag Test Suite

[JeromeJu]

Changes

Now that we have more per-feature flags in place, this PR adds the
per feature flag test. It currently utilize minimum end-to-end tests for
stable features while mocking stable, beta and alpha stability with
different test envs.

Currently this runs ~ 970s for my local env with 4 per-feature flags,
which is a reasonable amount since we are likely to be able to have a max
of ~ 12 flags within the timeframe of 60mins.

/kind misc

Submitter Checklist

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• Has Tests included if any functionality added or changed
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Release Notes

NONE

[chitrangpatel]

Thanks for this @JeromeJu !

Looks good to me.

Is there a plan to run this as part of our CI?
Since it only takes ~15 mins, I think we should.

[chitrangpatel]

/approve

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[JeromeJu]

Thanks for this @JeromeJu !

Looks good to me.

Is there a plan to run this as part of our CI? Since it only takes ~15 mins, I think we should.

Thanks Chitrang for the review.

Per discussion at tektoncd/plumbing#1629 (comment), let's have this in nightly first while we had some concern mentioned earlier. We could move it to be part of the per-build CI once we are actually having more per-feature flags(as the possibility of inter-correlation increases) and the nightly are proven to be effective.

[JeromeJu]

cc @tektoncd/core-maintainers can I have a lgtm for this change please?

[JeromeJu]

/test pull-tekton-pipeline-beta-integration-tests

[Yongxuanzhang]

/lgtm