Make private IP of the internal LB configurable

[nawazkh]

What type of PR is this?
/kind feature

What this PR does / why we need it:

• This PR is needed for updating Tilt workflow to spin up VM based templates with custom, non-overlapping Private IPs.

Which issue(s) this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when PR gets merged):
Fixes #5264

Special notes for your reviewer:

• Lets merge this PR once Use feature flag to create internal LB #5311 is merged.

TODOs:

• squashed commits
• includes documentation
• adds unit tests
• cherry-pick candidate

Release note:

feat APIServerILB: private IP of the internal LB can be customized

[k8s-ci-robot]

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[k8s-ci-robot]

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