- Set stream creator in serialize_request

TODO: 1. socket management 2. window mechanism

Fix compile error in thrift_protocol.cpp under macOS

Reduce the execution time of brpc_circuit_unittest

Basic support for http2

Simplify H2GlobalStreamCreator::OnCreatingStream & Not fail socket when running out of streams & misc changes

Fix a bug in Controlle.OnVersionedRPCReturned that successful response of non-backup request should be ignored

* Delete stream_creater() and make set_stream_creator can be called only once

the responsibility of stream_data and stream_creator more clearer