Convert 'id' and '_id' values in REST API tests to strings (#82681)

Follow-up from #77144 (comment) with converting id/_id to always be strings instead of integers. This makes the type value in the Elasticsearch specification be only string instead of string | number.

this change was generated using following command on ubuntu
find . -type f -name "*.yml" -print0 | xargs -0 sed -i -r 's/([^a-zA-Z0-9_\.]id|[^a-zA-Z0-9_]_id):(\s*)([0-9]+)/\1:\2"\3"/g'

modules/lang-expression/src/yamlRestTest/resources/rest-api-spec/test/lang_expression/20_search.yml

@@ -11,7 +11,7 @@ setup:
   - do:
       index:
         index:  test123
-        id:     1
+        id:     "1"
         body:   { age: 23 }
 
   - do: