static byte[] labelIkm(String label, byte[] ikm, byte[] suiteId) throws GeneralSecurityException {
    return Bytes.concat(HPKE_V1, suiteId, label.getBytes(UTF_8), ikm);
  }
Transforms {@code ikm} into labeled ikm using {@code label} and {@code suiteId} according to
{@code LabeledExtract()} defined in https://www.rfc-editor.org/rfc/rfc9180.html#section-4.

@throws GeneralSecurityException when byte concatenation fails.
java_src/src/main/java/com/google/crypto/tink/hybrid/internal/HpkeUtil.java