[type:feature] support dubbo protobuf serialization

[eye-gu]

support #5893 .
add dubbo protobuf serialization example

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[ForrestWang123]

Do you have any idea about the tech design? @eye-gu

I found genericService of Dubbo cannot be used in this scenario.
A possible way is to use a java code generator (e.g. Javassist) to generator the refrenceService at runtime.