gdb/python-config: replace deprecated distutils.sysconfig

gdb/python-config: replace deprecated distutils.sysconfig

When running the gdb/configure script on ubuntu 22.04 with
python-3.10.4, I see:

    checking for python... no
    checking for python3... /usr/bin/python3
    [...]/gdb/python/python-config.py:7: DeprecationWarning: The distutils package is deprecated and slated for removal in Python 3.12. Use setuptools or check PEP 632 for potential alternatives
      from distutils import sysconfig
    [...]/gdb/python/python-config.py:7: DeprecationWarning: The distutils.sysconfig module is deprecated, use sysconfig instead
      from distutils import sysconfig
    [...]/gdb/python/python-config.py:7: DeprecationWarning: The distutils package is deprecated and slated for removal in Python 3.12. Use setuptools or check PEP 632 for potential alternatives
      from distutils import sysconfig
    [...]/gdb/python/python-config.py:7: DeprecationWarning: The distutils.sysconfig module is deprecated, use sysconfig instead
      from distutils import sysconfig
    [...]/gdb/python/python-config.py:7: DeprecationWarning: The distutils package is deprecated and slated for removal in Python 3.12. Use setuptools or check PEP 632 for potential alternatives
      from distutils import sysconfig
    [...]/gdb/python/python-config.py:7: DeprecationWarning: The distutils.sysconfig module is deprecated, use sysconfig instead
      from distutils import sysconfig
    checking for python... yes

The distutils module is deprecated as per the PEP 632[1] and will be
removed in python-3.12.

This patch migrates gdb/python/python-config.py from distutils.sysconfig
to the sysconfig module[2].

The sysconfig module has has been introduced in the standard library in
python 3.2.  Given that support for python < 3.2 has been removed by
edae3fd6600f: "gdb/python: remove Python 2 support", this patch does not
need to support both implementations for backward compatibility.

Tested on ubuntu-22.04 and ubuntu 20.04.

[1] https://peps.python.org/pep-0632/
[2] https://docs.python.org/3/library/sysconfig.html

Change-Id: Id0df2baf3ee6ce68bd01c236b829ab4c0a4526f6