[EKS] [request]: While updating node group, offer option to update node group without creating new instances with new IPs

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**Tell us about your request**
What do you want us to build?
> While updating node group, could you offer an option to update the managed node group without creating new instances

**Which service(s) is this request for?**
> EKS

**Tell us about the problem you're trying to solve. What are you trying to do, and why is it hard?**
What outcome are you trying to achieve, ultimately, and why is it hard/impossible to do right now? What is the impact of not having this problem solved? The more details you can provide, the better we'll be able to understand and solve the problem.
> Since each node has an IP address, certain external integrators require one to share IPs to whitelist. Since the update terminates current instances and creates new IPs, this creates a tedious process of sharing new IPs with integrators.
Even for services like MongoDB which have network access options, you are required to add your Node IP.
Adding Load balancer IPs does not seem to be effective.
This approach would be similar to updating the the OS of a Windows/Linux EC2 instance

**Are you currently working around this issue?**
How are you currently solving this problem?
> Since we started using EKS, for now the node groups are not going to be updated or will be updated at a later time

**Additional context**
Anything else we should know?
> N/A

**Attachments**
If you think you might have additional information that you'd like to include via an attachment, please do - we'll take a look. (Remember to remove any personally-identifiable information.)

Start by reviewing the current EKS managed node group update behavior described in the issue, including why updates terminate instances and assign new IPs. Done means defining and implementing an update option that preserves existing instances and their IP addresses while updating the node group.

Written by the indexing model from the issue text.