add support for loadBalancerClass

[kishorj]

Issue

Fixes: #2466
Fixes: #2492

Description

Add support for service spec.loadBalancerClass. The load balancer class provides a similar mechanism to the current service annotation service.beta.kubernetes.io/aws-load-balancer-type: "external" to offload reconciling of load balancer from the kubernetes in-tree controller, but it is agnostic to the cloudprovider - KEP-1959 for details. The load balancer class is beta starting k8s 1.22.

The AWS Load Balancer controller will support the spec.loadBalancerClass starting v2.4.0 on k8s 1.22 and later. Here is the summary of the changes

• default LoadBalancerClass is service.k8s.aws/nlb, users can modify via controller command line flag --load-balancer-class
• with spec.loadBalancerClass, users no longer need to specify the annotation service.beta.kubernetes.io/aws-load-balancer-type on k8s 1.22 and later
• Target type defaults to instance for service with loadBalancerClass specified on supported k8s
• If loadBalancerClass is configured, when the user modifies the service type from LoadBalancer to something else, controller will deallocate the provisioned load balancer
• Provide a feature gate ServiceTypeLoadBalancerOnly which limits the controller to service of type LoadBalancer for NLB
• error out during reconcile for instance target if NodePort is not allocated

Tests:

• controller honors the spec.loadBalancerClass configuration on k8s 1.22
• controller works as expected on earlier k8s versions

Checklist

• Added tests that cover your change (if possible)
• Added/modified documentation as required (such as the README.md, or the docs directory)
• Manually tested
• Made sure the title of the PR is a good description that can go into the release notes

BONUS POINTS checklist: complete for good vibes and maybe prizes?! 🤯

• Backfilled missing tests for code in same general area 🎉
• Refactored something and made the world a better place 🌟

[k8s-ci-robot]

Skipping CI for Draft Pull Request.
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[M00nF1sh]

i think we can use service.k8s.aws/nlb to align with our IngressClass's ingress.k8s.aws/alb name. also it denotes it's a NLB :D

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 81.13208% with 10 lines in your changes missing coverage. Please review.

Project coverage is 53.51%. Comparing base (fe212ae) to head (bc9ec0f).
Report is 459 commits behind head on main.

Files with missing lines	Patch %	Lines
pkg/config/feature_gates.go	0.00%	3 Missing ⚠️
pkg/config/service_config.go	0.00%	2 Missing ⚠️
pkg/service/model_builder.go	81.81%	1 Missing and 1 partial ⚠️
pkg/service/service_utils.go	92.85%	1 Missing and 1 partial ⚠️
pkg/config/controller_config.go	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2489      +/-   ##
==========================================
+ Coverage   53.38%   53.51%   +0.13%     
==========================================
  Files         140      142       +2     
  Lines        7988     8026      +38     
==========================================
+ Hits         4264     4295      +31     
- Misses       3406     3412       +6     
- Partials      318      319       +1     

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[M00nF1sh]

/lgtm
/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: kishorj, M00nF1sh

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