Dubbo 3.0 provider doesn't register url param “serialization" to ZK.

[LaurenceLiZhixin]

• 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: 3.0.0-SNAPSHOT
• Operating System version: win10
• Java version: jdk8

An example of dubbo3 provider url registered to zk is:

tri://172.27.192.1:50051/com.apache.dubbo.sample.basic.IGreeter?anyhost=true&application=demo-provider&check=false&deprecated=false&dubbo=2.0.2&dynamic=true&generic=false&interface=com.apache.dubbo.sample.basic.IGreeter&methods=sayHello&release=3.0.0-SNAPSHOT&side=provider&threadname=DubboClientHandler-172.27.192.1:50051&threadpool=cached

Which doesn't contains "serialization" key.

But in dubbo/rpc/protocol/tri/TripleInvoker: doInvoke()

 protected Result doInvoke(final Invocation invocation) throws Throwable {
        RpcInvocation inv = (RpcInvocation)invocation;
        String methodName = RpcUtils.getMethodName(invocation);
        inv.setAttachment("path", this.getUrl().getPath());
        inv.setAttachment("serialization", this.getUrl().getParameter("serialization", "hessian2"));
        ...
}

It tries to read serialization type and set default to hessian2, which is confict with the real serialization type "protobuf"

[panxiaojun233]

It register url param “serialization" ,only by explicit configuration