Define the interface for NEG dual stack migration handler

[gauravkghildiyal]

/assign @swetharepakula

Notes for the reviewer

This change includes 3 commits. The last commit is just moving code from one location to another -- that piece of code makes a bulk of this PR and reviewing that again can be skipped.

[k8s-ci-robot]

Hi @gauravkghildiyal. 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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[aojea]

/ok-to-test

[swetharepakula]

/lgtm
/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: gauravkghildiyal, swetharepakula

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