Adding bulk-indexing and improving a bit the name indexing for bleve and elasticsearch (#16704)

* Adding bulk-indexing and improving a bit the name indexing for bleve and elasticsearch

* Update services/searchengine/bleveengine/bleve.go

Co-authored-by: Mario de Frutos Dieguez <mario@defrutos.org>

* Update store/sqlstore/file_info_store.go

Co-authored-by: Mario de Frutos Dieguez <mario@defrutos.org>

* Update store/sqlstore/file_info_store.go

Co-authored-by: Mario de Frutos Dieguez <mario@defrutos.org>

* Adding tests requested in the PR review

* fixing tests

* Adding a feature flag to avoid indexing files before the feature is released

* Fixing i18n

Co-authored-by: Mario de Frutos Dieguez <mario@defrutos.org>
Co-authored-by: Mattermod <mattermod@users.noreply.github.com>

i18n/en.json

@@ -5158,6 +5158,10 @@
     "id": "app.post.get_direct_posts.app_error",
     "translation": "Unable to get direct posts."
   },
+  {
+    "id": "app.post.get_files_batch_for_indexing.get.app_error",
+    "translation": "Unable to get the files batch for indexing."
+  },
   {
     "id": "app.post.get_flagged_posts.app_error",
     "translation": "Unable to get the flagged posts."
@@ -6078,6 +6082,10 @@
     "id": "bleveengine.purge_channel_index.error",
     "translation": "Failed to purge channel indexes."
   },
+  {
+    "id": "bleveengine.purge_file_index.error",
+    "translation": "Failed to purge file indexes."
+  },
   {
     "id": "bleveengine.purge_post_index.error",
     "translation": "Failed to purge post indexes."
@@ -6434,6 +6442,10 @@
     "id": "ent.elasticsearch.not_started.error",
     "translation": "Elasticsearch is not started"
   },
+  {
+    "id": "ent.elasticsearch.post.get_files_batch_for_indexing.error",
+    "translation": "Unable to get the files batch for indexing."
+  },
   {
     "id": "ent.elasticsearch.post.get_posts_batch_for_indexing.error",
     "translation": "Unable to get the posts batch for indexing."