unit-test for DeprecatedOptionalField
unit-test for DeprecatedOptionalField

Summary:
This unit-test is mostly copied from [folly:Optional unit-test](https://github.com/facebook/folly/blob/master/folly/test/OptionalTest.cpp), with following changes

1. Put it under `apache::thrift` namespace instead of `folly` namespace
2. Remove `in_place_t` constructor
3. Remove `make_optional` related unit-test
4. Modify HeterogeneousComparison unit-test so that it compares between `DeprecatedOptionalField<T>` and `folly::Optional<U>` (instead of `DeprecatedOptionalField<T>` and `DeprecatedOptionalField<U>`)
5. Remove boost::optional related comparison

Reviewed By: vitaut

Differential Revision: D20508190

fbshipit-source-id: cb9a447ba215039d5f9aafd40da937dbb191a12f

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