[Task] Move functionality out of nodegroup and nodegroup_service

[Himangini]

Description

This ticket to refactor functionality as suggested below and original ticket here

nodegroup.go

Methods for validating that managed nodegroup configurations are supported by the EKS versions. Seems reasonable & EKS related ✔️

func ValidateFeatureCompatibility(clusterConfig *api.ClusterConfig, kubeNodeGroups []KubeNodeGroup) error
func ValidateBottlerocketSupport(controlPlaneVersion string, kubeNodeGroups []KubeNodeGroup) error
func ValidateManagedNodesSupport(clusterConfig *api.ClusterConfig) error
func VersionSupportsManagedNodes(controlPlaneVersion string) (bool, error)
func ValidateWindowsCompatibility(kubeNodeGroups []KubeNodeGroup, controlPlaneVersion string) error
func ValidateKMSSupport(clusterConfig *api.ClusterConfig, eksVersion string) error
func SupportsWindowsWorkloads(nodeGroups []KubeNodeGroup) bool
func LogWindowsCompatibility(nodeGroups []KubeNodeGroup, clusterMeta *api.ClusterMeta)

Also contains a random stack-related func that should not be here ❎

func (c *ClusterProvider) GetNodeGroupIAM(stackManager manager.StackManager, ng *api.NodeGroup) error

nodegroup_service.go

Methods for translating managed nodegroup configuration into real information, e.g. taking instaceSelector fields and expanding them, resolving AMIs for when AMIFamily is specified etc. All of this code seems to apply to managed and unmanaged nodegroup, which means its not necessarily EKS specific knowledge. Consider moving ❎ , but it might also be okay to leave here ✔️ 🤷

func NewNodeGroupService(provider api.ClusterProvider, instanceSelector InstanceSelector) *NodeGroupService
func (m *NodeGroupService) NewAWSSelectorSession(provider api.ClusterProvider)
func (m *NodeGroupService) Normalize(nodePools []api.NodePool, clusterMeta *api.ClusterMeta) error
func (m *NodeGroupService) ExpandInstanceSelectorOptions(nodePools []api.NodePool, clusterAZs []string) error
func (m *NodeGroupService) ValidateLegacySubnetsForNodeGroups(spec *api.ClusterConfig, provider api.ClusterProvider) error

Also contains some stray validation logic that should/code be in nodegroup.go

func (m *NodeGroupService) ValidateExistingNodeGroupsForCompatibility(cfg *api.ClusterConfig, stackManager manager.StackManager) error