Driver classes (e.g. Manager, Cursor, ReadPreference, WriteResult) only implement the get_debug_info object handler. This allows them to produce output for var_dump(), but not var_export(), which depends on get_properties.

For the convenience of users that prefer to debug using var_export(), we should report the same information in get_properties as we currently do with get_debug_info today. Note that there is no need to implement __set_state() (we do not do so for BSON classes, which implemented get_properties in PHPC-460).