[Backport 8.x] Fix most ML APIs (#3289)

* updated discovery node class

* correct import

* fixes around ml

* more ml fixes, tentative discoverynode fix

* more ml fixes

* even more ml fixes

* other ml fixes

* modeling discovery node

* correct discovery nodes optionals

* correcting types

* removed deprecated params

* Update specification/ml/_types/TrainedModel.ts

Co-authored-by: Quentin Pradet <[email protected]>

* Update specification/ml/_types/TrainedModel.ts

Co-authored-by: Quentin Pradet <[email protected]>

* Update specification/ml/_types/TrainedModel.ts

Co-authored-by: Quentin Pradet <[email protected]>

* Update specification/ml/_types/TrainedModel.ts

Co-authored-by: Quentin Pradet <[email protected]>

* Update specification/ml/_types/TrainedModel.ts

Co-authored-by: Quentin Pradet <[email protected]>

* addressing reviews

* Update specification/ml/_types/inference.ts

Co-authored-by: Quentin Pradet <[email protected]>

* Update specification/ml/_types/inference.ts

Co-authored-by: Quentin Pradet <[email protected]>

* Update specification/ml/_types/inference.ts

Co-authored-by: Quentin Pradet <[email protected]>

* Update specification/ml/post_data/MlPostJobDataResponse.ts

Co-authored-by: Quentin Pradet <[email protected]>

* more review addressing

* merge fixes

---------

Co-authored-by: Quentin Pradet <[email protected]>
(cherry picked from commit ea3e9b6)

Co-authored-by: Laura Trotta <[email protected]>

Author: github-actions[bot]

output/openapi/elasticsearch-openapi.json

@@ -747,21 +747,6 @@
       ],
       "response": []
     },
-    "ml.get_trained_models": {
-      "request": [
-        "Request: missing json spec query parameter 'include_model_definition'"
-      ],
-      "response": []
-    },
-    "ml.put_job": {
-      "request": [
-        "Request: missing json spec query parameter 'ignore_unavailable'",
-        "Request: missing json spec query parameter 'allow_no_indices'",
-        "Request: missing json spec query parameter 'ignore_throttled'",
-        "Request: missing json spec query parameter 'expand_wildcards'"
-      ],
-      "response": []
-    },
     "ml.stop_datafeed": {
       "request": [
         "Request: missing json spec query parameter 'allow_no_datafeeds'"