AKS: Expose WithHelm and WithDashboard on AzureKubernetesEnvironmentResource

[mitchdenny]

Problem

WithHelm() and WithDashboard() are available on the inner KubernetesEnvironmentResource but not exposed on AzureKubernetesEnvironmentResource. Users cannot configure Helm chart settings (namespace, release name, chart version) or dashboard settings from the AKS builder.

Expected

var aks = builder.AddAzureKubernetesEnvironment("aks")
    .WithHelm(helm => helm.WithNamespace("my-ns").WithReleaseName("my-release"))
    .WithDashboard();

Related

Part of AKS hosting support (PR #16088)