### Description

Clusters can have thousands of ILM policies. 
`GET _ilm/policy` returns all of them and runs on the master node.

This proposes we chunk the response for better memory usage and clients experience.

Relates to https://github.com/elastic/elasticsearch/issues/96568
x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ilm/action/GetLifecycleAction.java
builder.endObject();
            }
            builder.endObject();
            return builder;
        }
        @Override
        public void writeTo(StreamOutput out) throws IOException {
            out.writeList(policies);
        }
        @Override
        public int hashCode() {
            return Objects.hash(policies);
        }
        @Override
        public boolean equals(Object obj) {
            if (obj == null) {
                return false;
            }
            if (obj.getClass() != getClass()) {
                return false;
            }
            Response other = (Response) obj;
            return Objects.equals(policies, other.policies);
        }
        @Override
        public String toString() {
            return Strings.toString(this, true, true);
        }
    }
    public static class Request extends AcknowledgedRequest<Request> {