[Triple] Optimize wrapper mode performance

# Background

The current triple protocol only supports pb serialization temporarily, it is recommended to use idl to generate stub.

However, there are still many users (especially java) users who are not used to using idl to generate stubs, so the triple protocol serializes the user objects into bytes in order to be compatible with the user habits of dubbo2, and then uses pb for packaging. Although this solution is feasible, serialization twice will lead to poor performance。

## Describe the proposal

In order to solve the above problems, we first have to make the triple protocol not strongly bound to pb.

We can use the content-type transfer serialization type to support different serialization protocols.

> But it should be noted that compatibility with the existing wrapper mode is required