Copy code.co_qualname on Python >= 3.11 (#423)

As of the changes to `linecache` in
python/cpython#117174, logging tracebacks
requires code objects to have a `co_qualname` attribute, which is true
for native Python code objects as of 3.11.  Adjust billiard's emulation
of them to match.

Spotted by pagure's tests in https://bugs.debian.org/1101621; analysis
and patch by Rebecca N. Palmer <[email protected]>.

Author: cjwatson

billiard/einfo.py

@@ -23,6 +23,7 @@ def __init__(self, code):
         self.co_stacksize = code.co_stacksize
         self.co_varnames = ()
         if sys.version_info >= (3, 11):
+            self.co_qualname = code.co_qualname
             self._co_positions = list(code.co_positions())
 
     if sys.version_info >= (3, 11):