Add ExtendedCall to PLCObject as a replacement of RemoteExec and reflect it in eRPC interface.

ExtendedCall is a generic remote procedure call that runtime code can register to and that IDE extensions can call.
For example a fieldbus extension can use ExtendedCall to browse the fieldbus devices connected to the runtime.

<?xml version='1.0' encoding='utf-8'?>
<ModbusTCPclient xmlns:xsd="http://www.w3.org/2001/XMLSchema" Remote_Port_Number="1502" Configuration_Name="Modbus TCP Client 0.0"/>