Remote Procedure Call (RPC)

https://github.com/apache/incubator-brpc/blob/master/community/cases.md

针对这个文件，提交PR，然后找我review即可。

更新过程：

1. 开一个issue，名字不妨为“xxx公司的brpc落地场景“
2. 修改这个文件（cases.md)
3. 提交PR

Let's support at least reading "b3" header from a single string, most commonly traceid-spanid-1
It would also be nice to support optionally writing this, especially in message providers or others with constrained environments.

Expected behavior

As discussed on openzipkin/b3-propagation#21 and first implemented here: https://github.com/openzipkin/brave/blob/master/brave/src/main/java/bra

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Issue Description
Write Unit Tests for some modules of Kitex, we mainly focus on Statement Coverage. The packages are shown below, you can choose and reply by comment.
Before you pick the task, please comply with the following requirements:

• The Unit Test you add must be meaningful.
  • It is used

AnnotatedServiceBindingBuilder and VirtualHostAnnotatedServiceBindingBuilder currently don't share a common interface for its methods, such as pathPrefix() and exceptionHandlers(). This means, a contributor can add a builder method to one builder but not to the other by mistake. By making both builder extend a new interface AnnotatedServiceConfigSetters, we could prevent such a mistake.