feat: implement strict multi-zone pod distribution for StatefulSets (PSCLOUD-64)

[abhikumar2204]

Adds comprehensive multi-zone pod distribution to prevent StatefulSet quorum
loss during zone failures in AKS, EKS, and GKE clusters.

Features:

• Strict topology spread constraints (maxSkew: 0) for multi-zone clusters
• Required pod anti-affinity to prevent same-zone co-location
• Automatic cluster zone detection with single-zone fallback
• Dedicated nodepool restriction for stateful workloads
• Configurable per-service (RabbitMQ, PostgreSQL) enablement

Changes:

• Add multi-zone transformers with restrictive constraints
• Add single-zone fallback transformers with relaxed constraints
• Implement automatic zone detection and conditional application
• Add nodepool restriction with workload.sas.com/class=stateful requirement
• Update VDM task pipeline to include multi-zone distribution
• Add comprehensive configuration variables with sensible defaults
• Update documentation with usage examples and behavior explanations

Transformers added:

• rabbitmq-zone-distribution.yaml (strict multi-zone)
• postgres-zone-distribution.yaml (strict multi-zone)
• multi-zone-pod-distribution.yaml (general StatefulSets)
• rabbitmq-single-zone-distribution.yaml (single-zone fallback)
• postgres-single-zone-distribution.yaml (single-zone fallback)

Configuration variables:

• V4_CFG_MULTI_ZONE_ENABLED (default: true)
• V4_CFG_MULTI_ZONE_AUTO_DETECT (default: true)
• V4_CFG_SINGLE_ZONE_FALLBACK (default: true)
• V4_CFG_STATEFUL_NODEPOOL_RESTRICTION (default: true)

Resolves: Multi-zone StatefulSet quorum protection requirements
Supports: AKS, EKS, GKE multi-zone and single-zone deployments
Backward compatible: Works with existing deployments without configuration changes