unpickler: refactor and reduce complexity
unpickler: refactor and reduce complexity

Break _restore() up into small single-page functions and
refactor it so that there is only a single exit point.

Signed-off-by: David Aguilar <9de348c050f7cd1ca590883733c4e531ce610bf4@gmail.com>

mandx/jsonpickle,dongguangming/jsonpickle,mandx/jsonpickle,dongguangming/jsonpickle,mandx/jsonpickle,dongguangming/jsonpickle,mandx/jsonpickle,dongguangming/jsonpickle