[Structure] Introduce Client/Server Mode

[OpcUa Support]

On the client side, the connection with the server side must be opened first. There will be a series of connection addresses, followed by a series of creation processes on the client side. The client side can ask the server side for some standard services, including establishing a dialogue and entering the address space to learn about the available content on the server side, read and write related variable values and data, dialog mode, read history, and close the dialog to end the connection.
The client-server subscription model can be used. The client can create an unlimited number of server subscriptions, including related variables. It can be used in SCADA if there are hundreds of devices, each link and subscription can be managed.