feat: Add Azure AKS composition

[pmady]

Description

Add a Crossplane 2.0 composition for provisioning Azure AKS clusters, similar to the existing EKS composition.

Proposed Features

• Azure VNet with subnets
• AKS cluster with managed node pools
• Azure CNI networking
• Integration with Azure AD for RBAC
• Support for multiple node pools

Acceptance Criteria

• Create crossplane-aks/ directory structure
• Implement XRD for AKS cluster
• Implement Composition with all required Azure resources
• Add example claim
• Add render tests
• Update main README with AKS documentation

Related

This is part of the roadmap to support multiple cloud providers.