Add scheduling strategies in CA

[walidghallab]

What type of PR is this?

/kind feature

What this PR does / why we need it:

Add scheduling strategies in CA.

To be more exact:
- An iterator to control the order of nodes to go through.
- An option to prefer the smallest number of iterations in case of
multiple matches, even if parallelism is enabled.

Why we need it? Because currently RunFiltersUntilPassingNode has only one scheduling strategy, which is to always start from the last node it tried. While this work in many cases, there are some cases where we don't want this behavior.

Adding this option is a way to:

• Provide some version of scoring nodes.
• Customize the order of nodes that scheduling go through.
• Due to parallelism, have a way to efficiently customize which node to return in case of multiple matches.

The only alternative that exist right now is to run CheckPredicates N times, but this is very slow because:

• It run prefilters N times (instead of just once), and prefilters are much slower than filters.
• Doesn't do parallelism.

In the current benchmarks, setting PreferredSmallestSteps to true has overhead of ~12%.
Other changes shouldn't have any noticeable effect.

Which issue(s) this PR fixes:

Fixes #

Special notes for your reviewer:

Does this PR introduce a user-facing change?

NONE

Additional documentation e.g., KEPs (Kubernetes Enhancement Proposals), usage docs, etc.:

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: walidghallab
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[k8s-ci-robot]

Hi @walidghallab. Thanks for your PR.

I'm waiting for a kubernetes 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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[walidghallab]

/cc x13n

[walidghallab]

/uncc elmiko

[walidghallab]

/uncc aleksandra-malinowska

[elmiko]

/ok-to-test

[k8s-ci-robot]

PR needs rebase.

Details

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes-sigs/prow repository.