Add Oxidized based direct decl parser

Summary: Convert `direct_decl_smart_constructors.rs` to use oxidized types, leaving `direct_decl_smart_constructors_obr.rs` on oxidized_by_ref. The oxidized ddp is only connected to the `ddp_test` command-line decl testing binary for now

Reviewed By: vassilmladenov

Differential Revision: D68772818

fbshipit-source-id: 7800bb616920d6e3e89345047d9b4b47949d04fa