Move C++ pickling builtins to their own boot module Pickle
Move C++ pickling builtins to their own boot module Pickle

* Rename pickle to pack and unpickle to unpack as they act on VirtualByteString.

eregon/mozart-graal,mistasse/mozart-graal,eregon/mozart-graal,mistasse/mozart-graal,mistasse/mozart-graal,mistasse/mozart-graal,eregon/mozart-graal,eregon/mozart-graal,mistasse/mozart-graal,eregon/mozart-graal,eregon/mozart-graal