Migrate to field_ref Thrift API
Migrate to field_ref Thrift API

Summary:
We are unifying C++ APIs for accessing optional and unqualified fields:
https://fb.workplace.com/groups/1730279463893632/permalink/2541675446087359/.

This diff migrates code from accessing data members generated from unqualified
Thrift fields directly to the `field_ref` API, i.e. replacing

```
thrift_obj.field
```

with

```
*thrift_obj.field_ref()
```

The `_ref` suffixes will be removed in the future once data members are private
and names can be reclaimed.

The output of this codemod has been reviewed in D20039637.

The new API is documented in
https://our.intern.facebook.com/intern/wiki/Thrift/FieldAccess/.

drop-conflicts

Reviewed By: simpkins

Differential Revision: D23465292

fbshipit-source-id: bb9df3ad183685fae28173da7275e6ecd34df048

facebook/wangle,facebook/wangle,facebook/wangle