build: scripts/config - update to kconfig-v5.6

Major changes include:
 - Much more readable reverse dependencies separated in groups
 - Improved recursive dependency report
 - More readable .config files: add comments to signal end of menus
 - More warnings for incorrect Config.in entries, such as a 'choice'
   default not contained in the 'choice'
 - Hability to properly display pseudographics with non-latin locales
 - Recursive dependencies can optionally be treated as errors

Changes from failed dcf3e63a35 attempt:
 - Recursive dependencies are treated as warnings by default
 - The option to treat them as errors is implemented as a command-line
   flag to scripts/config/conf instead of a compile-time definition
 - fixed handling of select with umnet dependencies

Cc: Petr Štetiar <ynezz@true.cz>
Cc: Jo-Philip Wich <jow@mein.io>
Signed-off-by: Eneas U de Queiroz <cotequeiroz@gmail.com>

scripts/config/.gitignore

@@ -1,15 +1,14 @@
-*.o
-conf*
-!conf*.c
-!conf*.h
-mconf*
-!mconf*.c
-!mconf*.h
-mconf_check
-*.*.c
-qconf*
-qconf*.moc
-!qconf*.cc
-!qconf*.h
-!images*.c
-.tmp_qtcheck
+#
+# Generated files
+#
+*.moc
+*conf-cfg
+
+#
+# configuration programs
+#
+conf
+mconf
+nconf
+qconf
+gconf