Fixed issue where pickle helpers didnt use new from_bytes with context

- Added with context to benchmarks that use with_bytes

capnp/lib/capnp.pyx

@@ -1099,7 +1099,8 @@ if getattr(_sys, 'subversion', [''])[0] == 'PyPy':
     from pickle_helper import _struct_reducer
 else:
     def _struct_reducer(schema_id, data):
-        return _global_schema_parser.modules_by_id[schema_id].from_bytes(data)
+        with _global_schema_parser.modules_by_id[schema_id].from_bytes(data) as msg:
+            return msg
 
 
 cdef class _DynamicStructReader:

capnp/lib/pickle_helper.py

@@ -3,4 +3,5 @@ import capnp
 
 def _struct_reducer(schema_id, data):
     'Hack to deal with pypy not allowing reduce functions to be "built-in" methods (ie. compiled from a .pyx)'
-    return capnp._global_schema_parser.modules_by_id[schema_id].from_bytes(data)
+    with capnp._global_schema_parser.modules_by_id[schema_id].from_bytes(data) as msg:
+        return msg