Generate 'use opcua::' instead of 'use crate::' when generating external nodeset

[gstvg]

• add opcua_server_crate cli option and pass it to from_xml config
• generate 'use' code based on opcua_server_crate config option

[locka99]

Hi sorry for not getting back but can you change the arg to --opcua-crate?

Otherwise seems fine.

[antiblue]

@gstvg: Any updates on this?

[locka99]

thanks for your patience sorry I was working on another branch - this is merged now