Support for thrift-py3 types
Support for thrift-py3 types

Summary:
So now that we generate typing information in the thrift compiler
I updated cython_library to support a 'types' argument for easily
integrating '.pyi' files to explain the types of compiled modules

I updated thrift_library to make use of the .pyi files that are generated

Making these part of cython_library made implementing thrift_library much
cleaner.

Reviewed By: yfeldblum

Differential Revision: D6394532

fbshipit-source-id: 4822628a3b4d2c9250dffd0fa4e0d13b2a9549a1

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