[3.13] gh-123339: Fix cases of inconsistency of __module__ and __firstlineno__ in classes (GH-123613) (#124735)

* Setting the __module__ attribute for a class now removes the
  __firstlineno__ item from the type's dict.
* The _collections_abc and _pydecimal modules now completely replace the
  collections.abc and decimal modules after importing them. This
  allows to get the source of classes and functions defined in these
  modules.
* inspect.findsource() now checks whether the first line number for a
  class is out of bound.
(cherry picked from commit 69a4063ca516360b5eb96f5432ad9f9dfc32a72e)