Once https://github.com/elastic/elasticsearch/issues/98503 is done, we can use our minimum version numbers in the SystemIndexMappingUpdate service instead of the old `Version` types. Mappings will be updated for a system index when all nodes have a matching descriptor mappings version for a system index, but this version is greater than what's stored in the mappings metadata.
server/src/internalClusterTest/java/org/elasticsearch/indices/TestSystemIndexDescriptor.java
public static final String INDEX_NAME = ".test-index";
    public static final String PRIMARY_INDEX_NAME = INDEX_NAME + "-1";
    public static final AtomicBoolean useNewMappings = new AtomicBoolean(false);
    public static final Settings SETTINGS = Settings.builder()
        .put(IndexMetadata.INDEX_NUMBER_OF_SHARDS_SETTING.getKey(), 1)
        .put(IndexMetadata.INDEX_AUTO_EXPAND_REPLICAS_SETTING.getKey(), "0-1")
        .put(IndexMetadata.SETTING_PRIORITY, Integer.MAX_VALUE)
        .build();
    TestSystemIndexDescriptor() {
        super(
            INDEX_NAME + "*",
            PRIMARY_INDEX_NAME,
            "Test system index",
            getOldMappings(),
            SETTINGS,
            INDEX_NAME,
            0,