In https://github.com/elastic/elasticsearch/pull/88639 we introduced a new setting that allows configuring a maximum headroom in disk watermarks that helps reducing the waste of disk space in large disks. The disk health indicator should take that new setting into account to avoid reporting issues when there's still room for new data in the cluster. 

https://github.com/elastic/elasticsearch/blob/6ec31ed1533e6aaf8fc6dabda5e419f5dce984fa/server/src/main/java/org/elasticsearch/health/metadata/HealthMetadata.java#L193-L199

Those calls should take into account the available max headroom.
server/src/main/java/org/elasticsearch/health/metadata/HealthMetadata.java
@Override
    public String toString() {
        return "HealthMetadata{diskMetadata=" + Strings.toString(diskMetadata) + '}';
    }
    /**
     * Contains the thresholds necessary to determine the health of the disk space of a node. The thresholds are determined by the elected
     * master.
     */
    public record Disk(
        RelativeByteSizeValue highWatermark,
        ByteSizeValue highMaxHeadroom,
        RelativeByteSizeValue floodStageWatermark,
        ByteSizeValue floodStageMaxHeadroom,
        RelativeByteSizeValue frozenFloodStageWatermark,
        ByteSizeValue frozenFloodStageMaxHeadroom
    ) implements ToXContentFragment, Writeable {
        public static final String TYPE = "disk";
        public static Version VERSION_SUPPORTING_HEADROOM_FIELDS = Version.V_8_5_0;
        private static final ParseField HIGH_WATERMARK_FIELD = new ParseField("high_watermark");
        private static final ParseField HIGH_MAX_HEADROOM_FIELD = new ParseField("high_max_headroom");
        private static final ParseField FLOOD_STAGE_WATERMARK_FIELD = new ParseField("flood_stage_watermark");
        private static final ParseField FLOOD_STAGE_MAX_HEADROOM_FIELD = new ParseField("flood_stage_max_headroom");
        private static final ParseField FROZEN_FLOOD_STAGE_WATERMARK_FIELD = new ParseField("frozen_flood_stage_watermark");
        private static final ParseField FROZEN_FLOOD_STAGE_MAX_HEADROOM_FIELD = new ParseField("frozen_flood_stage_max_headroom");
        static Disk readFrom(StreamInput in) throws IOException {
            RelativeByteSizeValue highWatermark = RelativeByteSizeValue.parseRelativeByteSizeValue(
                in.readString(),
                HIGH_WATERMARK_FIELD.getPreferredName()
            );
            RelativeByteSizeValue floodStageWatermark = RelativeByteSizeValue.parseRelativeByteSizeValue(