Prevent IsOneOf unused template specialization instantiation

Prevent IsOneOf unused template specialization instantiation

Summary:
Current `IsOneOf` implementation does unnecessary work because it instantiates all of the possible template specializations, even if type is same as the first of the tested ones. E.g.
`IsOneOf<char, char, int, float>` will instantiate:
```
IsOneOf<char, char, int, float>
IsOneOf<char, char, int>
IsOneOf<char, char>
IsOneOf<char>
```

With the proposed inheritance, compiler will stop initializing at the first match.
Closes https://github.com/facebook/folly/pull/643

Reviewed By: ericniebler

Differential Revision: D5482783

Pulled By: yfeldblum

fbshipit-source-id: 3d04c750ce72fa9b19b4d0588cccfb396a9e0715