bpo-35226: Fix equality for nested unittest.mock.call objects. (GH-10555)

Also refactor the call recording imolementation and add some notes
about its limitations.
(cherry picked from commit 8ca0fa9d2f4de6e69f0902790432e0ab2f37ba68)

Co-authored-by: Chris Withers <chris@withers.org>
6 files changed