Serialization ContentTypeId conflict between avro protocol and protocoluff protocol

[fitzf]

• I have searched the issues of this repository and believe that this is not a duplicate.
• I have checked the FAQ of this repository and believe that this is not a duplicate.

Environment

• Dubbo version: 2.7.2-SNAPSHOT
• Operating System version: OS X 10.14.4
• Java version: 1.8.0_202

Steps to reproduce this issue

1. [DUBBO] Serialization extension org.apache.dubbo.common.serialize.protostuff.ProtostuffSerialization has duplicate id to Serialization extension org.apache.dubbo.common.serialize.avro.AvroSerialization, ignore this Serialization extension

CodecSupport
static {
        Set<String> supportedExtensions = ExtensionLoader.getExtensionLoader(Serialization.class).getSupportedExtensions();
        for (String name : supportedExtensions) {
            Serialization serialization = ExtensionLoader.getExtensionLoader(Serialization.class).getExtension(name);
            byte idByte = serialization.getContentTypeId();
            if (ID_SERIALIZATION_MAP.containsKey(idByte)) {
                logger.error("Serialization extension " + serialization.getClass().getName()
                        + " has duplicate id to Serialization extension "
                        + ID_SERIALIZATION_MAP.get(idByte).getClass().getName()
                        + ", ignore this Serialization extension");
                continue;
            }
            ID_SERIALIZATION_MAP.put(idByte, serialization);
            ID_SERIALIZATIONNAME_MAP.put(idByte, name);
        }
    }

public class ProtostuffSerialization implements Serialization {
    @Override
    public byte getContentTypeId() {
        return 10;
    }
}

public class AvroSerialization implements Serialization {
    @Override
    public byte getContentTypeId() {
        return 10;
    }
}

[fitzf]

https://github.com/apache/incubator-dubbo/blob/9b11b7ac89c0d897220bc9b42b3e5e9c3eb708f2/dubbo-serialization/dubbo-serialization-avro/src/main/java/org/apache/dubbo/common/serialize/avro/AvroSerialization.java#L32
https://github.com/apache/incubator-dubbo/blob/9b11b7ac89c0d897220bc9b42b3e5e9c3eb708f2/dubbo-serialization/dubbo-serialization-protostuff/src/main/java/org/apache/dubbo/common/serialize/protostuff/ProtostuffSerialization.java#L39

[fitzf]

@ralf0131 @CrazyHZM PLZ

[CrazyHZM]

My mistake, I will fix it later, thank you.