Adding Kubelet cmd option to make system reserved CPU list specific

[jianzzha]

What type of PR is this?

Uncomment only one /kind <> line, hit enter to put that in a new line, and remove leading whitespaces from that line:

/kind api-change
/kind bug
/kind cleanup
/kind design
/kind documentation
/kind failing-test

/kind feature

/kind flake

What this PR does / why we need it:

Currently when --system-reserved or --kube-reserved is used, kubelet will reserve system resources and keep them from being used by user containers. What CPUs are reserved via these options are not easy to determine by the end users, even though the CPU selection algorithm make the selection in deterministic way.

For telco NFV use cases, when using static cpu manager policy, knowing explicitly what CPUs are reserved for system and what CPUs are used for user containers is very important. For example, if isolcpu are going to be defined on the kernel cmd line and used for NFV containers, they really should be used only by the NFV containers and not by the system threads. Therefore, providing an option to explicitly define the system reserved CPU list will make the planning job much easier and straightforward for such telco use cases.

This new cmd line option, --reserved-cpus, is to explicitly define the the cpu list that will be reserved for system. For example, if --reserved-cpus=0,1,2,3 is specified, then cpu 0,1,2,3 will be reserved for the system. On a system with 24 CPUs, the telco user may specify isolcpus=4-23 for the kernel option and use CPU 4-24 for the NFV containers.

When --reserved-cpus is specified together --system-reserved or --kube-reserved, the explicit CPU list specified by --reserved-cpus will supercede the CPUs requested via --system-reserved or --kube-reserved.

Which issue(s) this PR fixes:

Fixes #

Special notes for your reviewer:
cpu manager test cases failures are all inherited from release-1.16. I will submit a another PR to add new test cases around cpu manager.

Does this PR introduce a user-facing change?:

A new kubelet command line option, --reserved-cpus, is introduced to explicitly define the the CPU list that will be reserved for system. For example, if --reserved-cpus=0,1,2,3 is specified, then cpu 0,1,2,3 will be reserved for the system.  On a system with 24 CPUs, the user may specify isolcpus=4-23 for the kernel option and use CPU 4-24 for the user containers.

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

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@jianzzha: This cherry pick PR is for a release branch and has not yet been approved by the Patch Release Team.
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@jianzzha: Adding label do-not-merge/contains-merge-commits because PR contains merge commits, which are not allowed in this repository.
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[jianzzha]

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[jianzzha]

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