First CLB batch of changes

[georgeedward2000]

What type of PR is this?

/kind feature

What this PR does / why we need it:

This PR adds foundational infrastructure to support CIDR prefix-based NSG rules and prepares for the CLB DiffTracker Engine work. It includes:

1. Security Group Enhancements: Add support for CIDR prefix parameters in NSG rule methods (AddRuleForAllowedServiceTag, AddRuleForAllowedIPRanges, AddRuleForDenyAll), enabling more flexible network security management for pod-based load balancing.

2. New Utility Functions:

   • Case-insensitive string set implementation (pkg/util/sets/) for managing string collections
   • Comprehensive test coverage for utility functions

3. Configuration Additions:

   • Add PodCidrsIPv4 and PodCidrsIPv6 fields to support pod CIDR configuration
   • Add ServiceGatewayEnabled and related config fields for future service gateway support
   • Add helper methods: IsLBBackendPoolTypePodIP(), UseServiceLoadBalancer(), IsLBBackendPoolTypePodIPAndUseServiceLoadBalancer()

4. Constants and Templates:

   • Add LoadBalancerSKUService constant for service load balancer SKU
   • Add PodLabelServiceEgressGateway label constant
   • Add NatGatewayIDTemplate for NAT Gateway resource ID formatting
   • Fix capitalization: LoadBalancerBackendPoolConfigurationTypePODIP → LoadBalancerBackendPoolConfigurationTypePodIP

5. Test Infrastructure:

   • Add WithOnlyTCPPorts() and WithOnlyUDPPorts() test fixtures for service testing
   • Add RetainDestinationFromRules() method to security group helper for rule retention logic
   • Comprehensive test coverage for all new functionality (~1,200 new test lines)

This PR is the first in a series that will enable pod IP-based backend pools and the CLB DiffTracker Engine. All changes are backward compatible and do not affect existing functionality.

Does this PR introduce a user-facing change?

NONE

[k8s-ci-robot]

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[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: georgeedward2000
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[k8s-ci-robot]

Hi @georgeedward2000. Thanks for your PR.

I'm waiting for a github.com member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

Once the patch is verified, the new status will be reflected by the ok-to-test label.

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Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes-sigs/prow repository.