Expose performance options (v0.16)

[lcarva]

Changes

This allow admins to specify a few parameters to better suit their use of Chains.

--threads-per-controller controls the number of concurrent threads the Chains controller processes. The default value is 2.

--kube-api-burst controle the maximum burst for throttle.

--kube-api-qps controles the maximum QPS to the server from the client.

The approach taken here is the same one used by the Tekton Pipeline controller for the sake of consistency in the ecosystem.

Submitter Checklist

As the author of this PR, please check off the items in this checklist:

• [x] Has Docs included if any changes are user facing
• [ ] Has Tests included if any functionality added or changed
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• [x] Meets the Tekton contributor standards (including functionality, content, code)
• [x] Release notes block below has been updated with any user facing changes (API changes, bug fixes, changes requiring upgrade notices or deprecation warnings)
• [x] Release notes contains the string "action required" if the change requires additional action from users switching to the new release

Release Notes

Expose new performance parameters to control controller's execution. See docs at https://tekton.dev/docs/chains/performance for details.

[chitrangpatel]

/approve /lgtm

[lcarva]

/approve

[tekton-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: chitrangpatel, lcarva

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