[EKS] [request]: support SessionNameRaw in access entries

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**Tell us about your request**
We are migrating from the aws-auth ConfigMap, and we currently rely on the [SessionNameRaw](https://github.com/kubernetes-sigs/aws-iam-authenticator/blob/master/deploy/example.yaml#L130-L131) macro to map AWS SSO usernames (in our case, email addresses) to Kubernetes User names. We've tried to create an access entry via the console, and it doesn't seem like this macro is supported.

**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?**
Our AWS SSO users are provisioned automatically via SCIM with email address as the username. Currently `SessionName` transliterates `@` to `-`, which breaks our existing RBAC. We would need to either rewrite all of our RBAC to use the transliterated names, or continue to use the aws-auth ConfigMap for the foreseeable future.

**Are you currently working around this issue?**
We currently are still using a mix of access entries and the aws-auth ConfigMap.

**Attachments**
See error message from AWS console below:
![The specified username is invalid: "{{SessionNameRaw}}" is an invalid macro. Valid macros include: [{{AccessKeyID}}, {{AccountID}}, {{SessionName}}]](https://github.com/aws/containers-roadmap/assets/790279/218b3406-044d-4387-b2d0-f74cc3e10304)

Start by reviewing the linked aws-iam-authenticator example and the AWS console error shown in the issue. The request concerns supporting the SessionNameRaw macro in EKS access entries so SCIM-provisioned email usernames remain usable for Kubernetes RBAC; done means the macro is accepted and preserves the raw session name.

Written by the indexing model from the issue text.