`CheckHeaderConfig` forces `Values` be defined, but should be optional

### Report

According to https://learn.microsoft.com/en-us/azure/api-management/check-header-policy the `CheackHeader` policy does not require values.

We use this policy to check the presence of a header, but not enforce a specific value. For example:

context.CheckHeader(new CheckHeaderConfig()
{
Name = "x-correlation-id",
FailCheckErrorMessage = "Bad request. Missing correlation id in headers",
FailCheckHttpCode = 400,
IgnoreCase = false,
Values = []
});

### Expected Behavior

The `Values` param does not need to be specified, or an empty array be permitted - in either case the resultant XML `` element would not contain any `` elements

### Actual Behavior

`Values` is required, so must be provided. When it is, but left as empty, then the following error is encountered on compilation:

> error APIM2007: Required 'Values' parameter for 'check-header' policy is empty but needs at least one element

Due to the above error the resultant XML does not include the `` output

### Steps to Reproduce the Problem

This should be a minimum viable example:

```CSHARP
using Microsoft.Azure.ApiManagement.PolicyToolkit.Authoring;
using Microsoft.Azure.ApiManagement.PolicyToolkit.Authoring.Expressions;

namespace SomeNamespace
{
[Document(Scope = DocumentScope.Api)]
public class AllOperations : IDocument
{
public void Inbound(IInboundContext context)
{
context.Base();

context.CheckHeader(new CheckHeaderConfig()
{
Name = "x-correlation-id",
FailCheckErrorMessage = "Bad request. Missing correlation id in headers",
FailCheckHttpCode = 400,
IgnoreCase = false,
Values = []
});
}
}
}

```

### Component

Compiler

### Version

Main

### Contact Details

_No response_

### Additional Information

_No response_