`GetEnvironmentVariableValuesAsync ` doesn't properly resolve `HostUrl`

### Is there an existing issue for this?

- [x] I have searched the existing issues

### Describe the bug

`resource.GetEnvironmentVariableValuesAsync()` doesn't pass through `AppHost:ContainerHost` down into `ProcessEnvironmentVariableValuesAsync`, and so always resolves host references as `host.docker.internal`

### Expected Behavior

I'd expect it to honour `AppHost:ContainerHost`, but with this extension method on `IResource`, it doesn't have any reference to the Configuration. This seems very similar to #9787 , which makes me wonder if the API itself is the problem - needing to be on a supporting service rather than an extension method on `IResource`. So whilst it's a good approximation, there are a number of edge cases where it will resolve values differently.

### Steps To Reproduce

_No response_

### Exceptions (if any)

_No response_

### .NET Version info

_No response_

### Anything else?

https://github.com/CommunityToolkit/Aspire/pull/853#discussion_r2347359579
https://github.com/CommunityToolkit/Aspire/pull/853#discussion_r2347555676