[Feature] Pod Subnet Static Block Allocation dual-stack

Public Preview ETA: Aug 2026
GA ETA: Oct 2026

*ETAs are estimations and are subject to change

**Is your feature request related to a problem? Please describe.**
IPv6 is a requirement for compliance reasons as well as high scale IP usage. While overlay exists, the only other AKS flat networking mode that supports IPv6 is kubenet which is being deprecated.

https://learn.microsoft.com/en-us/azure/aks/configure-azure-cni-static-block-allocation should support the creation of dual-stack Prefix on NICv6 clusters.

xref: https://github.com/Azure/AKS/issues/4389

**Describe the solution you'd like**
An AKS cluster should support IPv6 enabled flat pod networking.

**Describe alternatives you've considered**
N/A

**Additional context**
N/A