MM-6992 Added highlighting to elasticsearch results (#8861)

* MM-6992 Added highlighting to elasticsearch results

* Added a unique type for post search matches

* Fixed Elasticsearch matches not being sent through API

i18n/en.json

@@ -4278,6 +4278,10 @@
     "id": "ent.elasticsearch.search_posts.search_failed",
     "translation": "Search failed to complete"
   },
+  {
+    "id": "ent.elasticsearch.search_posts.parse_matches_failed",
+    "translation": "Failed to parse search result matches"
+  },
   {
     "id": "ent.elasticsearch.search_posts.unmarshall_post_failed",
     "translation": "Failed to decode search results"