Switch to HexEncoding from ByteStringUtils

import android.security.keystore.recovery.InternalRecoveryServiceException;

import android.security.keystore.recovery.LockScreenRequiredException;

import android.security.keystore.recovery.RecoveryController;

import android.util.ByteStringUtils;

import com.android.internal.annotations.VisibleForTesting;

import libcore.util.HexEncoding;

import java.security.SecureRandom;

import java.security.UnrecoverableKeyException;

import java.util.Optional;

    private String generateId() {

        byte[] id = new byte[BACKUP_KEY_SUFFIX_LENGTH_BITS / BITS_PER_BYTE];

        mSecureRandom.nextBytes(id);

        return BACKUP_KEY_ALIAS_PREFIX + ByteStringUtils.toHexString(id);

        return BACKUP_KEY_ALIAS_PREFIX + HexEncoding.encodeToString(id);

    }

    /** Constructs a {@link RecoverableKeyStoreSecondaryKeyManager}. */