[Task] Remove support for EKS 1.23

[Himangini]

Description

As per the calendar for Amazon EKS end of support 11 Oct 2024 is the extended end of support for Kubernetes version 1.23
See https://endoflife.date/amazon-eks

We need to remove support for 1.23 and modify any relevant docs wherever possible.
Reference PR - see here

[sbdtu5498]

/assign. Will pick it up when the time comes. Let me know if are we waiting for AWS to announce the exact date or if it is something related to Eksctl's internal schedule.

[TiberiuGC]

Since after this change we'll only support EKS 1.24 and upwards, we also need to remove any logic related to dockershim deprecation.

References (i.e. some code areas that need to account for this change):

eksctl/userdocs/src/usage/container-runtime.md

Lines 3 to 6 in 02c41d5

	!!! warning
	Starting with Kubernetes version `1.24`, dockershim support has been deprecated. Therefore, if you create a cluster using `eksctl` on version `1.24` or higher, the information below no longer applies, and the only supported container runtime is `containerd`. Trying to set it otherwise will return a validation error. Additionally, AL2023 AMIs only support `containerd` regadless of K8s version.
	At some point, we will completely remove the option to set `containerRuntime` in config file, together with the support for older Kubernetes versions support (i.e. `1.22` or `1.23`).

eksctl/pkg/apis/eksctl.io/v1alpha5/defaults.go

Lines 260 to 282 in 02c41d5

	func setContainerRuntimeDefault(ng *NodeGroup, clusterVersion string) {
	if ng.ContainerRuntime != nil {
	return
	}
	if ng.AMIFamily == NodeImageFamilyAmazonLinux2023 {
	ng.ContainerRuntime = aws.String(ContainerRuntimeContainerD)
	return
	}
	// since clusterVersion is standardised beforehand, we can safely ignore the error
	if isDockershimDeprecated, _ := utils.IsMinVersion(DockershimDeprecationVersion, clusterVersion); isDockershimDeprecated {
	ng.ContainerRuntime = aws.String(ContainerRuntimeContainerD)
	return
	}
	if IsWindowsImage(ng.AMIFamily) {
	ng.ContainerRuntime = aws.String(ContainerRuntimeDockerForWindows)
	return
	}
	ng.ContainerRuntime = aws.String(ContainerRuntimeDockerD)
	}

eksctl/pkg/apis/eksctl.io/v1alpha5/validation.go

Lines 916 to 935 in 02c41d5

	if ng.ContainerRuntime != nil {
	if ng.AMIFamily == NodeImageFamilyAmazonLinux2023 && *ng.ContainerRuntime != ContainerRuntimeContainerD {
	return fmt.Errorf("only %s is supported for container runtime on %s nodes", ContainerRuntimeContainerD, NodeImageFamilyAmazonLinux2023)
	}
	if *ng.ContainerRuntime != ContainerRuntimeDockerD && *ng.ContainerRuntime != ContainerRuntimeContainerD && *ng.ContainerRuntime != ContainerRuntimeDockerForWindows {
	return fmt.Errorf("only %s, %s and %s are supported for container runtime", ContainerRuntimeContainerD, ContainerRuntimeDockerD, ContainerRuntimeDockerForWindows)
	}
	if clusterVersion := cfg.Metadata.Version; clusterVersion != "" {
	isDockershimDeprecated, err := utils.IsMinVersion(DockershimDeprecationVersion, clusterVersion)
	if err != nil {
	return err
	}
	if *ng.ContainerRuntime != ContainerRuntimeContainerD && isDockershimDeprecated {
	return fmt.Errorf("only %s is supported for container runtime, starting with EKS version %s", ContainerRuntimeContainerD, Version1_24)
	}
	}
	if ng.OverrideBootstrapCommand != nil {
	return fmt.Errorf("overrideBootstrapCommand overwrites container runtime setting; please use --container-runtime in the bootsrap script instead")
	}
	}

[TiberiuGC]

@sbdtu5498 I'm removing the good first issue label as removing support for 1.23 involves these ⬆️ specific changes.