feat: cache and use Linux private packages for kubctl and kubelet.

[daxakp]

What type of PR is this?
feature

What this PR does / why we need it:
This PR downloads and saves private packages for kubelet and kubectl. This packages will be used at run-time when needed.
The PR adds two build-time variables as below:

Build Variables:

name: PRIVATE_PACKAGES_URL
value: comma separated list of packages, for example: https://private-acs-mirror.azureedge.net/kubernetes/v1.25.6-hotfix.20230612/binaries/kubernetes-node-linux-amd64.tar.gz,https://private-acs-mirror.azureedge.net/kubernetes/v1.28.0/binaries/kubernetes-node-linux-amd64.tar.gz

name: AZURE_MSI_RESOURCE_ID
value: MSI resource ID that is created already and has sufficient roles assigned to be able to access the above private packages from the packer VM.

• Kubernetes packages are cached on disk at: /opt/kubernetes/downloads/private-packages
  At run-time, given a Kube version, the cached version if exists is used by default.
  For example,
  kubernetes package from https://private-acs-mirror.azureedge.net/kubernetes/v1.28.0/binaries/kubernetes-node-linux-amd64.tar.gz is saved as /opt/kubernetes/downloads/private-packages/v1.28.0.tar.gz

Which issue(s) this PR fixes:

Fixes #

Requirements:

• uses conventional commit messages
• includes documentation
• adds unit tests
• tested upgrade from previous version

Special notes for your reviewer:

Release note:

none

[coveralls]

Pull Request Test Coverage Report for Build 7484217224

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.02%) to 79.356%

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Totals
Change from base Build 7483530675:	0.02%
Covered Lines:	2291
Relevant Lines:	2887

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💛 - Coveralls

[ganeshkumarashok]

would it be useful to do validation of the private package URLs?

[Bryce-Soghigian]

Approved on the karpenter side, shouldn't be any breaking changes since the url passed in is an optional parameter and functions fine when we pass in an empty string.

Please wait on node sig approval as well before merging :)