Remove implementation specific function name of EventDispatcher

Some of the member functions of EventDispatcher are implementation specific, for example AddEpollOut.

We need to change that specific function name and adopt more general name then we can easily support brpc to more platforms.

Locate EventDispatcher and inspect the implementation-specific member functions, starting with AddEpollOut. Inventory the names that prevent support for more platforms and determine the general naming needed; done means the dispatcher uses platform-neutral names and can support brpc on more platforms.

Written by the indexing model from the issue text.