Specify name on enrich.get_policy as list type (#50217)

This commit updates the enrich.get_policy API to specify name
as a list, in line with other URL parts that accept a comma-separated
list of values.

In addition, update the get enrich policy API docs
to align the URL part name in the documentation with
the name used in the REST API specs.

(cherry picked from commit 94f6f946ef283dc93040e052b4676c5bc37f4bde)

docs/reference/ingest/apis/enrich/get-enrich-policy.asciidoc

@@ -50,7 +50,7 @@ GET /_enrich/policy/my-policy
 [[get-enrich-policy-api-request]]
 ==== {api-request-title}
 
-`GET /_enrich/policy/<enrich-policy>`
+`GET /_enrich/policy/<name>`
 
 `GET /_enrich/policy`
 
@@ -66,7 +66,7 @@ include::put-enrich-policy.asciidoc[tag=enrich-policy-api-prereqs]
 [[get-enrich-policy-api-path-params]]
 ==== {api-path-parms-title}
 
-`<enrich-policy>`::
+`<name>`::
 +
 --
 (Optional, string)

x-pack/plugin/src/test/resources/rest-api-spec/api/enrich.get_policy.json

@@ -11,8 +11,8 @@
           "methods": [ "GET" ],
           "parts": {
             "name": {
-              "type" : "string",
+              "type" : "list",
-              "description" : "The name of the enrich policy"
+              "description" : "A comma-separated list of enrich policy names"
             }
           }
         },