[ML] adding new PUT trained model vocabulary endpoint (#77387)

This commit removes the ability to set the vocabulary location in the model config.
This opts instead for sane defaults to be set and used. Wrapping this up in an
API.

The index is now always the internally managed .ml-inference-native index
and the document ID is always <model_id>_vocabulary

This API only works for pytorch/nlp type models.

docs/reference/ml/df-analytics/apis/index.asciidoc

@@ -4,6 +4,7 @@ include::put-dfanalytics.asciidoc[leveloffset=+2]
 include::put-trained-models-aliases.asciidoc[leveloffset=+2]
 include::put-trained-models.asciidoc[leveloffset=+2]
 include::put-trained-model-definition-part.asciidoc[leveloffset=+2]
+include::put-trained-model-vocabulary.asciidoc[leveloffset=+2]
 //UPDATE
 include::update-dfanalytics.asciidoc[leveloffset=+2]
 //DELETE

docs/reference/ml/df-analytics/apis/ml-df-analytics-apis.asciidoc

@@ -20,6 +20,7 @@ You can use the following APIs to perform {infer} operations:
 
 * <<put-trained-models>>
 * <<put-trained-model-definition-part>>
+* <<put-trained-model-vocabulary>>
 * <<put-trained-models-aliases>>
 * <<delete-trained-models>>
 * <<delete-trained-models-aliases>>

docs/reference/ml/df-analytics/apis/put-trained-model-vocabulary.asciidoc

@@ -0,0 +1,45 @@
+[role="xpack"]
+[testenv="basic"]
+[[put-trained-model-vocabulary]]
+= Create trained model vocabulary API
+[subs="attributes"]
+++++
+<titleabbrev>Create trained model vocabulary</titleabbrev>
+++++
+
+Creates a trained model vocabulary.
+This is only supported on NLP type models.
+
+experimental::[]
+
+[[ml-put-trained-model-vocabulary-request]]
+== {api-request-title}
+
+`PUT _ml/trained_models/<model_id>/vocabulary/`
+
+
+[[ml-put-trained-model-vocabulary-prereq]]
+== {api-prereq-title}
+
+Requires the `manage_ml` cluster privilege. This privilege is included in the
+`machine_learning_admin` built-in role.
+
+
+[[ml-put-trained-model-vocabulary-path-params]]
+== {api-path-parms-title}
+
+`<model_id>`::
+(Required, string)
+include::{es-repo-dir}/ml/ml-shared.asciidoc[tag=model-id]
+
+[[ml-put-trained-model-vocabulary-request-body]]
+== {api-request-body-title}
+
+`vocabulary`::
+(array)
+The model vocabulary. Must not be empty.
+
+////
+[[ml-put-trained-model-vocabulary-example]]
+== {api-examples-title}
+////