No schema check for the property "attachPolicyARNs"

[hassanSRE]

What happened?
When creating a simple config file to create a nodegroup that includes the property attachPolicyARNs, if the attach policy arn property is not written exactly like "attachPolicyARNs:", it is ignore. Example:

---
apiVersion: eksctl.io/v1alpha5
kind: ClusterConfig

metadata:
  name: cluster-name
  region: ap-southeast-2

nodeGroups:
  - name: ng-name
    iam:
      attachPolicyARNs:
        - arn:aws:iam::aws:policy/AmazonEKSWorkerNodePolicy
        - arn:aws:iam::aws:policy/AmazonEKS_CNI_Policy
        - arn:aws:iam::ACCOUNT:policy/SOME_POLICY

The above will be ignored and all 3 default node policies will be added instead
Note the above property attachPolicyArns isn't exactly the same as attachPolicyARNs. Changing the above property to the exact described schema attachPolicyARNs works fine

What you expected to happen?
If the property attachPolicyARNs added is not adhering to the case sensitivity, it should throw a schema validation error instead of just ignoring it

How to reproduce it?
Add the following in the config schema:
nodeGroups:

• name: ng-name
  ...
  iam:
  attachPolicyArns: ## <----- Note that this isn't exactly like attachPolicyARNs
  - arn:aws:iam::aws:policy/AmazonEKSWorkerNodePolicy
  - arn:aws:iam::aws:policy/AmazonEKS_CNI_Policy
  - arn:aws:iam::ACCOUNT:policy/NAME_OF_POLIC

Versions
Please paste in the output of these commands:

$ eksctl version 0.28.1
$ kubectl version v1.15.10-eks-bac369

[michaelbeaumont]

Duplicate of #753