(aws-ec2): InterfaceVpcEndpointAwsService is missing "eks-proxy" endpoint

### Describe the bug

The AWS European Sovereign Cloud has an interface VPC endpoint called `eks-proxy` which is not included in the current version of the VPC endpoint constants.

### Regression Issue

- [ ] Select this option if this issue appears to be a regression.

### Last Known Working CDK Library Version

_No response_

### Expected Behavior

The `InterfaceVpcEndpointAwsService` class should contain a field for the `eks-proxy` interface VPC endpoint.

### Current Behavior

The `InterfaceVpcEndpointAwsService` class does not contain a field for the `eks-proxy` interface VPC endpoint.

### Reproduction Steps

Try to deploy the `eks-proxy` VPC endpoint using a static constant from `InterfaceVpcEndpointAwsService`.

### Possible Solution

Add an `EKS_PROXY` field to `InterfaceVpcEndpointAwsService`.

### Additional Information/Context

_No response_

### AWS CDK Library version (aws-cdk-lib)

2.261.0

### AWS CDK CLI version

2.1129.0

### Node.js Version

v24.16.0

### OS

MacOS 26.5.2

### Language

TypeScript

### Language Version

_No response_

### Other information

_No response_

Start by locating the InterfaceVpcEndpointAwsService class in the aws-cdk repository and inspect how its existing interface VPC endpoint constants are defined. Add the missing eks-proxy entry following the class's established naming and value conventions, then verify that the class exposes the requested endpoint constant.

Written by the indexing model from the issue text.