More defensive guards against invalid code points in ant Preferences

[mbien]

followup on #6094

Once Preferences is loaded containing U+0000 in a key, it can't be used anymore since even removing that key (e.g via clear()) will throw IAE.

What we can do however is to remove and recreate the Preferences node.

example output with this change active:

WARNING [org.apache.tools.ant.module.api.IntrospectedInfo]: skipping malformed key; pref path: /org/apache/tools/ant/module/customDefs, msg: Key contains code point U+0000
WARNING [org.apache.tools.ant.module.AntSettings]: recreating preferences node due to code point U+0000

tested by corrupting the config file using this script:

    static void main() throws java.io.IOException {
        String path = "netbeans/nbbuild/testuserdir/config/Preferences/org/apache/tools/ant/module/customDefs.properties";
        Files.writeString(
                Path.of(path),
                "\u0000",
                StandardOpenOption.APPEND
        );
    }

closes #8941
targets delivery

[matthiasblaesing]

This is really ugly and IMHO a JDK issue. Anyway for us we have no real alternative, so I don't see an alternative.

[mbien]

agreed. At least clear() should be implemented in a way so that it can reliably clear preferences.