Attach Policy to AWS Elasticsearch
Unfortunately, you can't use your policy in IP policy for an ES domain.
Let me elaborate a bit on this, as I think there is a confusion between resource-based policies, such as IP policies for the ES domain, and identity-based policies for IAM users, roles or groups. The differences are explained in the AWS docs.
In short, you policy arn:aws:iam::0000000:policy/Whitelister is, so called, managed-policy. The managed polices can only be attached to IAM identity which can be IAM user, group or role. They can't be attached to resource-based policies.