Fix test cases in consul 1.21 on GKE 1.34

[shani34]

Test cases fixes

1. fixes related to dns

• GKE-aware DNS handling: The code now detects GKE and uses stubDomains to extend DNS safely without breaking kube-dns behavior.
• Clean config backups: Metadata like resourceVersion is stripped before restore, preventing conflicts during cleanup.
• Correct DNS restarts: The right DNS deployment (coredns, kube-dns, or rke2-coredns) is detected and restarted to avoid stale DNS.

2. Fixes related to Vault

• Explicit pod CIDR allocation:
ip_allocation_policy.cluster_ipv4_cidr_block assigns a deterministic, non-overlapping pod IP range (10.100.0.0/14 split per cluster), which is critical for multi-cluster communication.
• Expanded firewall source ranges:
source_ranges now allows traffic not only from the other cluster’s pod CIDR but also from its VPC subnet CIDR, ensuring pod-to-pod and node-level traffic works reliably across clusters.
• Targeted firewall scoping:
target_tags restricts these firewall rules to only the Consul/K8s nodes, improving security while still enabling required cross-cluster traffic.