container_type member alias for sorted-vector types
container_type member alias for sorted-vector types

Summary: [Folly] container_type member alias for `sorted_vector_set` and `sorted_vector_map`, following the protocol from `std::queue`, `std::priority_queue`, and `std::stack` container adaptors.

Reviewed By: vitaut

Differential Revision: D15194108

fbshipit-source-id: 91332478c66779690f415d598b99274b8ee52df4

facebook/folly,facebook/folly,facebook/folly,facebook/folly,facebook/folly