OpenAPI: Minimal API unused Path parameters are not emitted in the OpenAPI

### Is there an existing issue for this?

- [x] I have searched the existing issues

### Describe the bug

The following unit test fails because the parameters are `null`.

```csharp
[Fact]
public async Task SupportsUnusedRouteParametersFromMinimalApis()
{
var source = """
using System;
using System.Threading.Tasks;
using System.Collections.Generic;
using Microsoft.AspNetCore.Builder;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.AspNetCore.Http;

var builder = WebApplication.CreateBuilder();

builder.Services.AddOpenApi();

var app = builder.Build();

app.MapGet("/{userId}", RouteHandlerExtensionMethods.Get);

app.Run();

public static class RouteHandlerExtensionMethods
{
/// The id of the user.
public static string Get()
{
return "Hello, World!";
}
}
""";

var generator = new XmlCommentGenerator();
await SnapshotTestHelper.Verify(source, generator, out var compilation);
await SnapshotTestHelper.VerifyOpenApi(compilation, document =>
{
var path = document.Paths["/{userId}"].Operations[HttpMethod.Get];
Assert.NotEmpty(path.Parameters);
Assert.Equal("The id of the user.", path.Parameters[0].Description);
});
}
```

### Expected Behavior

The unused path parameter `{userId}` should be emitted on the operation or on the path as a parameter (that is `document.Paths["/{userId}"].Parameters`).

### Steps To Reproduce

_No response_

### Exceptions (if any)

_No response_

### .NET Version

10.0.100-rc.1.25420.111

### Anything else?

Found while fixing #63757