[MM-63513] Turn Cross team search feature flag into a setting option (#30518)

* feat: Add EnableCrossTeamSearch configuration option to ServiceSettings

* feat: Add EnableCrossTeamSearch configuration option to ServiceSettings

* feat: Enable cross-team search by default

* include old FF in client config

server/platform/services/telemetry/telemetry.go

@@ -526,6 +526,7 @@ func (ts *TelemetryService) trackConfig() {
 		"enable_channel_viewed_messages":                          *cfg.ServiceSettings.EnableChannelViewedMessages,
 		"time_between_user_typing_updates_milliseconds":           *cfg.ServiceSettings.TimeBetweenUserTypingUpdatesMilliseconds,
 		"cluster_log_timeout_milliseconds":                        *cfg.ServiceSettings.ClusterLogTimeoutMilliseconds,
+		"enable_cross_team_search":                                *cfg.ServiceSettings.EnableCrossTeamSearch,
 		"enable_post_search":                                      *cfg.ServiceSettings.EnablePostSearch,
 		"minimum_hashtag_length":                                  *cfg.ServiceSettings.MinimumHashtagLength,
 		"enable_user_statuses":                                    *cfg.ServiceSettings.EnableUserStatuses,