python3: fix PACKAGECONFIG handling

* it was changed from sysconf_dis to mods_disabled in:
  https://git.openembedded.org/openembedded-core/diff/meta/recipes-devtools/python/python3/0017-setup.py-do-not-report-missing-dependencies-for-disa.patch?id=7347556b18b45c5f9afc2cade565a75c95876914



  but unfortunately this doesn't work as mods_disabled set by remove_configured_extensions
  can contain only extensions which were disabled, as this list:
  self.extensions: ['_struct', 'array', '_contextvars', 'math', 'cmath', 'time', '_datetime', '_zoneinfo', '_random', '_bisect', '_heapq', '_pickle', 'atexit', '_json', '_lsprof', 'unicodedata', '_opcode', '_asyncio', '_abc', '_queue', '_statistics', 'fcntl', 'pwd', 'grp', 'spwd', 'select', 'parser', 'mmap', 'syslog', '_xxsubinterpreters', 'audioop', '_csv', '_posixsubprocess', '_testcapi', '_testinternalcapi', '_testbuffer', '_testimportmultiple', '_testmultiphase', '_xxtestfuzz', '_curses', '_curses_panel', '_crypt', '_socket', '_ssl', '_hashlib', '_sha256', '_sha512', '_md5', '_sha1', '_blake2', '_sha3', '_sqlite3', 'termios', 'resource', 'ossaudiodev', 'nis', 'zlib', 'binascii', '_bz2', '_lzma', 'pyexpat', '_elementtree', '_multibytecodec', '_codecs_kr', '_codecs_jp', '_codecs_cn', '_codecs_tw', '_codecs_hk', '_codecs_iso2022', '_decimal', '_ctypes_test', '_posixshmem', '_multiprocessing', '_uuid', 'xxlimited', '_ctypes']

  while PACKAGECONFIG in python3 usually uses this to disable _dbm, _gdbm or runtime modules.

* without this change the do_install will fail (based on check_build_completeness.py log.do_compile) with:
  | ERROR: Execution of '/OE/build/oe-core/tmp-glibc/work/x86_64-linux/python3-native/3.9.0-r0/temp/run.do_install.69743' failed with exit code 1:
  | The necessary bits to build these optional modules were not found:
  | _dbm                  _gdbm                 readline

Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>