### Description

We now support storing KNN vectors as part of our indexed data.  These vectors should be included in the disk usage API.
server/src/main/java/org/elasticsearch/action/admin/indices/diskusage/IndexDiskUsageStats.java
}
    @Override
    public void writeTo(StreamOutput out) throws IOException {
        out.writeMap(fields, StreamOutput::writeString, (o, v) -> v.writeTo(o));
        out.writeVLong(indexSizeInBytes);
    }
    PerFieldDiskUsage total() {
        final PerFieldDiskUsage total = new PerFieldDiskUsage();
        for (PerFieldDiskUsage value : fields.values()) {
            total.add(value);
        }
        return total;
    }
    Map<String, PerFieldDiskUsage> getFields() {
        return fields;
    }
    long getIndexSizeInBytes() {
        return indexSizeInBytes;
    }
    private static void checkByteSize(long bytes) {
        if (bytes < 0) {
            throw new IllegalArgumentException("Bytes must be non-negative; got " + bytes);
        }
    }
    private PerFieldDiskUsage getOrAdd(String fieldName) {
        Objects.requireNonNull(fieldName, "fieldName must be non-null");
        return fields.computeIfAbsent(fieldName, k -> new PerFieldDiskUsage());
    }
    public void addInvertedIndex(String fieldName, long bytes) {
        checkByteSize(bytes);