MM-57786 Fix Shared Channels plugin api (#26753)

* always ping on plugin registration; SharedChannel.IsValid allow no team for GM

* wait for services to start before ping

* ping plugin remotes synchronously on startup

* remove the waitForInterClusterServices stuff

* don't set remoteid when inviting remote to channel

* Update server/public/model/remote_cluster_test.go

Co-authored-by: Ibrahim Serdar Acikgoz <serdaracikgoz86@gmail.com>

* address review comments

---------

Co-authored-by: Mattermost Build <build@mattermost.com>
Co-authored-by: Ibrahim Serdar Acikgoz <serdaracikgoz86@gmail.com>

server/platform/services/sharedchannel/sync_send_remote.go

@@ -107,6 +107,10 @@ func (scs *Service) syncForRemote(task syncTask, rc *model.RemoteCluster) error
 		if scr, err = scs.server.GetStore().SharedChannel().SaveRemote(scr); err != nil {
 			return fmt.Errorf("cannot auto-create shared channel remote (channel_id=%s, remote_id=%s): %w", task.channelID, rc.RemoteId, err)
 		}
+		scs.server.Log().Log(mlog.LvlSharedChannelServiceDebug, "Auto-invited remote to channel (BitflagOptionAutoInvited)",
+			mlog.String("remote", rc.DisplayName),
+			mlog.String("channel_id", task.channelID),
+		)
 	} else if err != nil {
 		return err
 	}