chore(ec2): billing interface vpc endpoint (#32103)

### Issue # (if applicable)

None

### Reason for this change

New interface VPC endpoint has released.

### Description of changes

Add BILLING `InterfaceVpcEndpointService`.

### Description of how you validated changes

Execute descrive endpoint CLI:

```sh
❯ aws ec2 describe-vpc-endpoint-services --filters Name=service-type,Values=Interface Name=owner,Values=amazon --region us-east-1 --query ServiceNames | grep billing
    "com.amazonaws.us-east-1.billing", // newly added
    "com.amazonaws.us-east-1.billingconductor",
```

### Checklist
- [x] My code adheres to the [CONTRIBUTING GUIDE](https://github.com/aws/aws-cdk/blob/main/CONTRIBUTING.md) and [DESIGN GUIDELINES](https://github.com/aws/aws-cdk/blob/main/docs/DESIGN_GUIDELINES.md)

----

*By submitting this pull request, I confirm that my contribution is made under the terms of the Apache-2.0 license*

packages/aws-cdk-lib/aws-ec2/lib/vpc-endpoint.ts

@@ -305,6 +305,7 @@ export class InterfaceVpcEndpointAwsService implements IInterfaceVpcEndpointServ
   public static readonly BEDROCK_AGENT = new InterfaceVpcEndpointAwsService('bedrock-agent');
   public static readonly BEDROCK_AGENT_RUNTIME = new InterfaceVpcEndpointAwsService('bedrock-agent-runtime');
   public static readonly BEDROCK_RUNTIME = new InterfaceVpcEndpointAwsService('bedrock-runtime');
+  public static readonly BILLING = new InterfaceVpcEndpointAwsService('billing');
   public static readonly BILLING_AND_COST_MANAGEMENT_FREETIER = new InterfaceVpcEndpointAwsService('freetier', 'aws.api');
   public static readonly BILLING_AND_COST_MANAGEMENT_TAX = new InterfaceVpcEndpointAwsService('tax');
   public static readonly BILLING_CONDUCTOR = new InterfaceVpcEndpointAwsService('billingconductor');