[EKS] [request]: EBS volume encryption support _without_ custom launch templates

### Community Note

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**Tell us about your request**
What do you want us to build?
A bool for enabling node EBS volume encryption _without_ the need for a custom LT

**Which service(s) is this request for?**
This could be Fargate, ECS, EKS, ECR
EKS and EKS Fargate

**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.

For a "managed" service, this should be a given option. It's not hard, but it's maintenance that others need to be aware of that isn't exactly obvious.

**Are you currently working around this issue?**
How are you currently solving this problem?

A custom LT but this prevents touchless upgrades.

**Additional context**
Anything else we should know?

This is _not_ duplicated like you have closed all other issues asking for this.

**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.)

No source files, tests, or implementation entry points are identified in this roadmap request. Start by clarifying the expected EKS and EKS Fargate behavior for enabling EBS encryption without a custom launch template, then define acceptance criteria with maintainers; done means the option supports touchless upgrades as requested.

Written by the indexing model from the issue text.