[Aider assisted]: Templatize rest of the elasticsearch translation strings (#29582)

After https://github.com/mattermost/mattermost/pull/29209, there were some more
strings which were left out. Sending another PR to fix all of them.

The config validation strings are made generic for simplicity, because they
are called before the search backend is started, and even though you could
check for the config setting, it forces the code order. Therefore, changed
the words to just say "Search" for simplicity.

I tried to use Aider initially for a little while, but ended up fighting
a lot with the search/replace and having to repeat myself over and over again
to get it to do the refactoring. Eventually gave up and did rest of the changes
myself.

```release-note
NONE
```

server/i18n/en.json

@@ -7786,7 +7786,7 @@
   },
   {
     "id": "ent.elasticsearch.generic.disabled",
-    "translation": "Elasticsearch search is not enabled on this server"
+    "translation": "{{.Backend}} search is not enabled on this server"
   },
   {
     "id": "ent.elasticsearch.getAllChannelMembers.error",
@@ -7822,11 +7822,11 @@
   },
   {
     "id": "ent.elasticsearch.indexer.do_job.parse_end_time.error",
-    "translation": "Elasticsearch indexing worker failed to parse the end time"
+    "translation": "{{.Backend}} indexing worker failed to parse the end time"
   },
   {
     "id": "ent.elasticsearch.indexer.do_job.parse_start_time.error",
-    "translation": "Elasticsearch indexing worker failed to parse the start time"
+    "translation": "{{.Backend}} indexing worker failed to parse the start time"
   },
   {
     "id": "ent.elasticsearch.indexer.index_batch.nothing_left_to_index.error",
@@ -7834,11 +7834,11 @@
   },
   {
     "id": "ent.elasticsearch.max_version.app_error",
-    "translation": "Elasticsearch version {{.Version}} is higher than max supported version of {{.MaxVersion}}"
+    "translation": "{{.Backend}} version {{.Version}} is higher than max supported version of {{.MaxVersion}}"
   },
   {
     "id": "ent.elasticsearch.not_started.error",
-    "translation": "Elasticsearch is not started"
+    "translation": "{{.Backend}} is not started"
   },
   {
     "id": "ent.elasticsearch.post.get_files_batch_for_indexing.error",
@@ -7866,7 +7866,7 @@
   },
   {
     "id": "ent.elasticsearch.search_channels.disabled",
-    "translation": "Elasticsearch searching is disabled on this server"
+    "translation": "{{.Backend}} searching is disabled on this server"
   },
   {
     "id": "ent.elasticsearch.search_channels.search_failed",
@@ -7878,7 +7878,7 @@
   },
   {
     "id": "ent.elasticsearch.search_files.disabled",
-    "translation": "Elasticsearch files searching is disabled on this server"
+    "translation": "{{.Backend}} files searching is disabled on this server"
   },
   {
     "id": "ent.elasticsearch.search_files.search_failed",
@@ -7890,7 +7890,7 @@
   },
   {
     "id": "ent.elasticsearch.search_posts.disabled",
-    "translation": "Elasticsearch searching is disabled on this server"
+    "translation": "{{.Backend}} searching is disabled on this server"
   },
   {
     "id": "ent.elasticsearch.search_posts.parse_matches_failed",
@@ -7914,19 +7914,19 @@
   },
   {
     "id": "ent.elasticsearch.start.get_server_version.app_error",
-    "translation": "Failed to get Elasticsearch server version."
+    "translation": "Failed to get {{.Backend}} server version."
   },
   {
     "id": "ent.elasticsearch.start.parse_server_version.app_error",
-    "translation": "Failed to parse Elasticsearch server version."
+    "translation": "Failed to parse {{.Backend}} server version."
   },
   {
     "id": "ent.elasticsearch.stop.already_stopped.app_error",
-    "translation": "Elasticsearch is already stopped."
+    "translation": "{{.Backend}} is already stopped."
   },
   {
     "id": "ent.elasticsearch.test_config.indexing_disabled.error",
-    "translation": "Elasticsearch is disabled."
+    "translation": "{{.Backend}} is disabled."
   },
   {
     "id": "ent.elasticsearch.test_config.license.error",
@@ -8854,23 +8854,23 @@
   },
   {
     "id": "model.config.is_valid.elastic_search.aggregate_posts_after_days.app_error",
-    "translation": "Elasticsearch AggregatePostsAfterDays setting must be a number greater than or equal to 1."
+    "translation": "Search AggregatePostsAfterDays setting must be a number greater than or equal to 1."
   },
   {
     "id": "model.config.is_valid.elastic_search.bulk_indexing_batch_size.app_error",
-    "translation": "Elasticsearch Bulk Indexing Batch Size must be at least {{.BatchSize}}."
+    "translation": "Search Bulk Indexing Batch Size must be at least {{.BatchSize}}."
   },
   {
     "id": "model.config.is_valid.elastic_search.connection_url.app_error",
-    "translation": "Elasticsearch ConnectionUrl setting must be provided when Elasticsearch indexing is enabled."
+    "translation": "Search ConnectionUrl setting must be provided when indexing is enabled."
   },
   {
     "id": "model.config.is_valid.elastic_search.enable_autocomplete.app_error",
-    "translation": "Elasticsearch EnableIndexing setting must be set to true when Elasticsearch EnableAutocomplete is set to true"
+    "translation": "Search EnableIndexing setting must be set to true when Elasticsearch EnableAutocomplete is set to true"
   },
   {
     "id": "model.config.is_valid.elastic_search.enable_searching.app_error",
-    "translation": "Elasticsearch EnableIndexing setting must be set to true when Elasticsearch EnableSearching is set to true"
+    "translation": "Search EnableIndexing setting must be set to true when Elasticsearch EnableSearching is set to true"
   },
   {
     "id": "model.config.is_valid.elastic_search.ignored_indexes_dash_prefix.app_error",
@@ -8882,15 +8882,15 @@
   },
   {
     "id": "model.config.is_valid.elastic_search.live_indexing_batch_size.app_error",
-    "translation": "Elasticsearch Live Indexing Batch Size must be at least 1."
+    "translation": "Search Live Indexing Batch Size must be at least 1."
   },
   {
     "id": "model.config.is_valid.elastic_search.posts_aggregator_job_start_time.app_error",
-    "translation": "Elasticsearch PostsAggregatorJobStartTime setting must be a time in the format \"hh:mm\"."
+    "translation": "Search PostsAggregatorJobStartTime setting must be a time in the format \"hh:mm\"."
   },
   {
     "id": "model.config.is_valid.elastic_search.request_timeout_seconds.app_error",
-    "translation": "Elasticsearch Request Timeout must be at least 1 second."
+    "translation": "Search Request Timeout must be at least 1 second."
   },
   {
     "id": "model.config.is_valid.email_batching_buffer_size.app_error",