[DOCS] Move machine learning results definitions into APIs

[lcawl]

This PR adds tagged sections that contain descriptions of the machine learning results resource properties. It removes the results resource definitions page (https://www.elastic.co/guide/en/elasticsearch/reference/master/ml-results-resource.html) and uses the shared tagged sections to put that information directly into the appropriate APIs.

NOTE: As a result of these changes, users no longer need to flip between the results resource page and the API pages to find all the necessary details. However, from a maintenance stand-point, it means that when parameters or properties are added or removed, each of the affected APIs' pages must be updated appropriately.

Preview:

• http://elasticsearch_50257.docs-preview.app.elstc.co/guide/en/elasticsearch/reference/master/ml-get-bucket.html
• http://elasticsearch_50257.docs-preview.app.elstc.co/guide/en/elasticsearch/reference/master/ml-get-category.html
• http://elasticsearch_50257.docs-preview.app.elstc.co/guide/en/elasticsearch/reference/master/ml-get-influencer.html
• http://elasticsearch_50257.docs-preview.app.elstc.co/guide/en/elasticsearch/reference/master/ml-get-overall-buckets.html
• http://elasticsearch_50257.docs-preview.app.elstc.co/guide/en/elasticsearch/reference/master/ml-get-record.html

[elasticmachine]

Pinging @elastic/es-docs (>docs)

[elasticmachine]

Pinging @elastic/ml-core (:ml)

[szabosteve]

LGTM!