[MM-4819] Add MinimumHashtagLength config (#10248)

#### Summary
Add `MinimumHashtagLength` config

#### Ticket Link
#9156 
https://mattermost.atlassian.net/browse/MM-4819

#### Checklist
N/A

app/diagnostics.go

@@ -278,6 +278,7 @@ func (a *App) trackConfig() {
 		"time_between_user_typing_updates_milliseconds":           *cfg.ServiceSettings.TimeBetweenUserTypingUpdatesMilliseconds,
 		"cluster_log_timeout_milliseconds":                        *cfg.ServiceSettings.ClusterLogTimeoutMilliseconds,
 		"enable_post_search":                                      *cfg.ServiceSettings.EnablePostSearch,
+		"minimum_hashtag_length":                                  *cfg.ServiceSettings.MinimumHashtagLength,
 		"enable_user_statuses":                                    *cfg.ServiceSettings.EnableUserStatuses,
 		"close_unused_direct_messages":                            *cfg.ServiceSettings.CloseUnusedDirectMessages,
 		"enable_preview_features":                                 *cfg.ServiceSettings.EnablePreviewFeatures,