Use qualified Python names in metadata if available

[olupton]

co_qualname is the equivalent of __qualname__ in Python code.
For a member function

class A:
  def b(self):
    pass

then the co_name of b was b, and the co_qualname of it is A.b.
These locations are propagated to XLA and the metadata of the compiled graph.
Depending on the coding style, b can be a very generic name (run, or whatever) with the useful information contained in the class name, A. In that case, having both in the metadata is more informative.

Unfortunately before Python 3.11 then the qualified name was not available through the code object.

See #18764 for an example of the co_name-based metadata.

cc: @nouiz

[hawkinsp]

Looks good to me! Thanks for the PR.

(The only thing I'm wondering is: do we have a test for this? If so, it might need updating. Let's see what CI says.)