feat: support in-place NLB subnet changes

[dwj300]

Fixes #41418.

Rollback Plan

If a change needs to be reverted, we will publish an updated version of the library.

Changes to Security Controls

Are there any changes to security controls (access controls, encryption, logging) in this pull request? If so, explain.

Description

Relations

Closes #41418

References

Output from Acceptance Testing

% make testacc TESTS='TestAccELBV2LoadBalancer_NetworkLoadBalancer_delete' PKG=elbv2

...

[github-actions]

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[github-actions]

✅ Thank you for correcting the previously detected issues! The maintainers appreciate your efforts to make the review process as smooth as possible.