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

This used to be the case on Python 2.  Commit
212b590e118e3650b596917021ed9612a918180b 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.