add options to tune concurrency, qps and burst

[ajaysundark]

Description

Add flags to the controller to tune controller-runtime knobs for scalability

Related Issue

None

Type of Change

/kind feature

Testing

Manual test runs

Checklist

• make test passes
• make lint passes

Does this PR introduce a user-facing change?

Yes, adds command-flags to tune concurrency, qps and burst -- https://cluster-api.sigs.k8s.io/developer/core/tuning#runtime-tuning-options

Relevant for our ongoing scalability work.

add new commandline-flags for tuning concurrency, qps and burst limits

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[kubernetes-prow]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: ajaysundark

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[vitorfloriano]

I took this branch for a spin and verified that the tuning works.

I ran a manual test with a 1000-node kwok cluster without any parameters and NRC added all the taints in about 2m55s:

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The same manual test with --node-concurrent-reconciles 20 --kube-api-burst 1000 --kube-api-qps 50** is performed in 1m21s (about half the time w/o any tuning):

I'm still learning how to query Prometheus, but I think I got this right.

**Just picked these numbers randomly.

[ajaysundark]

@Karthik-K-N @vitorfloriano addressed your comments, ptal when you are available.

[ajaysundark]

/retest