isDatapointAnomaly(dataIndex) should be cached or memoized

The following discussion from !16530 (merged) should be addressed:

• @pslaughter started a discussion:

  suggestion (non-blocking): I think we have a potential to pre-cache or memoize some of these values. Nothing we need to handle in this MR, but might be interested to handle in a follow up. If we create an issue for it, a community contributor might actually pick it up 😄