[AKS] add AzureLinux3 ossku to preview (#36337)

* feat: add AzureLinux3 ossku

* chore: update description

Author: lilypan26

specification/containerservice/resource-manager/Microsoft.ContainerService/aks/preview/2025-07-02-preview/managedClusters.json

@@ -8213,6 +8213,7 @@
         "CBLMariner",
         "Mariner",
         "AzureLinux",
+        "AzureLinux3",
         "Windows2019",
         "Windows2022",
         "Windows2025",
@@ -8236,6 +8237,10 @@
             "value": "AzureLinux",
             "description": "Use AzureLinux as the OS for node images. Azure Linux is a container-optimized Linux distro built by Microsoft, visit https://aka.ms/azurelinux for more information."
           },
+          {
+            "value": "AzureLinux3",
+            "description": "Use AzureLinux3 as the OS for node images. Azure Linux is a container-optimized Linux distro built by Microsoft, visit https://aka.ms/azurelinux for more information. For limitations, visit https://aka.ms/aks/node-images. For OS migration guidance, see https://aka.ms/aks/upgrade-os-version."
+          },
           {
             "value": "CBLMariner",
             "description": "Deprecated OSSKU. Microsoft recommends that new deployments choose 'AzureLinux' instead."