[`Setting.versionSetting`](https://github.com/elastic/elasticsearch/blob/0652a5915586abbcdfdfffa91a391740f0147752/server/src/main/java/org/elasticsearch/common/settings/Setting.java#L1275) (only used by index compatibility setting) does not use the `Validator` passed in - its just discarded. Looks like it's been like this since it was introduced by https://github.com/elastic/elasticsearch/pull/83264 in 8.2.0.

Enabling this causes some tests to fail. Enabling this may cause problems for indexes that have a wonky setting already applied.
server/src/main/java/org/elasticsearch/common/settings/Setting.java
public GroupKey(String key) {
            super(key);
            if (key.endsWith(".") == false) {
                throw new IllegalArgumentException("key must end with a '.'");
            }
        }
        @Override
        public boolean match(String toTest) {
            return Regex.simpleMatch(key + "*", toTest);
        }
    }
    public static final class ListKey extends SimpleKey {
        private final Pattern pattern;
        public ListKey(String key) {
            super(key);
            this.pattern = Pattern.compile(Pattern.quote(key) + "(\\.\\d+)?");
        }
        @Override
        public boolean match(String toTest) {
            return pattern.matcher(toTest).matches();
        }
    }
    /**
     * A key that allows for static pre and suffix. This is used for settings
     * that have dynamic namespaces like for different accounts etc.
     */
    public static final class AffixKey implements Key {