Add ModeHandler::IsListModeBase() and MC_LIST
Keep lists of mode handlers by type
Send ListModeBase modes implicitly on channel sync

Remove Module::ProtoSendMode() and ListModeBase::DoSyncChannel()
Split ProtocolInterface::SendMetaData() into multiple functions
Pass an interface to the OnSync hooks

Remove Module::ProtoSendMetaData()
m_services_account Remove OnDecodeMetaData handler

Override StringExtItem::unserialize() instead
Remove redundant parameter.clear()s from mode handlers