bpo-31457: Don't omit inner ``process()`` calls with nested LogAdapters (GH-4044) (#6568)

This used to be the case on Python 2.  Commit
212b590e changed the implementation for Python
3, making the `log()` method of LogAdapter call `logger._log()` directly.  This
makes nested log adapters not execute their ``process()`` method.  This patch
fixes the issue.

Also, now proxying `name`, too, to make `repr()` work with nested log adapters.

New tests added.
(cherry picked from commit ce9e6254)
Co-authored-by: Łukasz Langa <lukasz@langa.pl>

Misc/NEWS.d/next/Library/2017-10-18-19-05-17.bpo-31457.KlE6r8.rst

+If nested log adapters are used, the inner ``process()`` methods are no
+longer omitted.