Make ThriftServerAsyncProcessorFactory perfectly forwarding
Make ThriftServerAsyncProcessorFactory perfectly forwarding

Summary:
Consider,
```name=foo.thrift
service Base {
  void foo();
}
service Derived extends Base {}
```
The generated `MethodMetadata` for `foo` is NOT the same between `Base` and `Derived` - they are incompatible.

Therefore, `ThriftServerAsyncProcessorFactory<BaseSvIf>(std::make_shared<DerivedSvIf>())` is not safe.

{D35603486 (https://github.com/facebook/fbthrift/commit/86aa1fa713b81f9746efc37bf70ef9c13062d73f)} implemented `createMethodMetadata` here which triggered this.

This diff fixes it by making the class perfectly forward all methods and ignore the template parameter completely. When possible, this class should be removed completely.

Reviewed By: sazonovkirill

Differential Revision: D35801117

fbshipit-source-id: 6a5552a95bf75fc23f828ca0f0727d0a31610be1

facebook/fbthrift,facebook/fbthrift,facebook/fbthrift,facebook/fbthrift,facebook/fbthrift,facebook/fbthrift,facebook/fbthrift,facebook/fbthrift,facebook/fbthrift