Remove mstch_py3_container_type and two py3 factories
Remove mstch_py3_container_type and two py3 factories

Summary:
`mstch_py3_container_type` doesn't do anything useful, only registers `containerType:flat_name` which isn't used anywhere. Remove it.

Move caching logic from `py3_type_factory` to `py3_type` and remove `py3_type_factory` and `py3_service_factory`.

Replace two cache lookups with a single one.

Rename `cachedProps_` to `cached_props_` per naming conventions while at it.

Reviewed By: nanshu

Differential Revision: D38519827

fbshipit-source-id: 31d95504d74e41fa79d3c6b2d35012cbc917703c

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