fix: include Generic config specs in EKS cluster API

[dkoshkin]

What problem does this PR solve?:
Stacked on #1297

This fixes the generic handlers for EKS clusters by properly exposing the GenericClusterConfigSpec API in EKSClusterConfig.

The following fields are still aspirational and are not properly supported in the handlers for EKS, but they can be.

	// +kubebuilder:validation:Optional
	Proxy *HTTPProxy `json:"proxy,omitempty"`

	// +kubebuilder:validation:Optional
	// +kubebuilder:validation:MaxItems=32
	ImageRegistries []ImageRegistry `json:"imageRegistries,omitempty"`

	// +kubebuilder:validation:Optional
	GlobalImageRegistryMirror *GlobalImageRegistryMirror `json:"globalImageRegistryMirror,omitempty"`

But these are working and I've added broken tests to verify before fixing the API.

	// +kubebuilder:validation:Optional
	// +kubebuilder:validation:MaxItems=32
	Users []User `json:"users,omitempty"`

	// NTP defines the NTP configuration for the cluster.
	// +kubebuilder:validation:Optional
	NTP *NTP `json:"ntp,omitempty"`

Which issue(s) this PR fixes:
Fixes #

How Has This Been Tested?:

Special notes for your reviewer: