Allow store password to be null when saving a PKCS12 KeyStore

A DESCRIPTION OF THE PROBLEM :
With the changes made for JDK-8076190 it is possible to load PKCS12 keystores without integrity protection and no encrypted certificates.
However, it appears creating such keystore is not easily possible because passing `null` as password to KeyStore.store(OutputStream, char[]) uses an empty char[] as password instead. To work around this, the user would have to change the System / Security properties "keystore.pkcs12.macAlgorithm" and "keystore.pkcs12.certProtectionAlgorithm" which could affect concurrently running PKCS12 keystore operations.

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Use the code provided below. The keystore is stored with `null` as password.

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
Loading the keystore with `null` as password works and all certificates are accessible.
ACTUAL -
Loading the keystore with `null` works (because integrity check is skipped, as expected), but no certificates are accessible.

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import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.nio.charset.StandardCharsets;
import java.security.KeyStore;
import java.security.KeyStoreException;
import java.security.NoSuchAlgorithmException;
import java.security.cert.CertificateException;
import java.security.cert.CertificateFactory;
import java.security.cert.X509Certificate;

public class Pkcs12PasswordlessTest {
    private static final String CERT_PEM =
        "-----BEGIN CERTIFICATE-----\n" +
        "MIICADCCAWmgAwIBAgIEdyF6ojANBgkqhkiG9w0BAQsFADAyMQ0wCwYDVQQKEwREZW1vMQ0wCwYDVQQLEwREZW" +
        "1vMRIwEAYDVQQDEwlEZW1vIGNlcnQwIBcNMTkwODMxMTMwODM2WhgPMjEwOTA1MTkxMzA4MzZaMDIxDTALBgNV" +
        "BAoTBERlbW8xDTALBgNVBAsTBERlbW8xEjAQBgNVBAMTCURlbW8gY2VydDCBnzANBgkqhkiG9w0BAQEFAAOBjQ" +
        "AwgYkCgYEAo5ULhB6DQo8A9EH1Zxl29eK2In4Tqt3dzNAY3MQULoV6wCWUfc8dJa5RnZiOGJUxgnLPBU/UgjTi" +
        "IJFohzrlHjmhWsdnbJtYA51raEG3JKNDakhBCmgoTue8veMlwegIgElV/dzfGl+HtG5wI4aJkONT0Jg8bzLOex" +
        "rNvn588X8CAwEAAaMhMB8wHQYDVR0OBBYEFH/vBQPBrtPS83M2CM4p2PPZSn1HMA0GCSqGSIb3DQEBCwUAA4GB" +
        "AAPM8WxouFVgP+T2oy55gqLwW3CKOvfueIX3xyAAcS2rpMayHdJ7yAQrd00kvXy+bs1eAayXyNRawT2EIX1qv7" +
        "9wNn4qtmVnk8t+J9ckkoWpUCGw45F5/Q1EhVxMKjJBNbik2k1k/1SXksneIgONp+AkzISRFtq+p3J9KpVO9g2m" +
        "\n-----END CERTIFICATE-----";
    
    public static void main(String[] args) throws Exception {
        byte[] keyStoreData = createKeyStoreData();
        KeyStore keyStore = KeyStore.getInstance("pkcs12");
        
        /*
         * Keystore was stored with null as integrity protection password, so loading it
         * with null as password should work and certificates should be accessible.
         * However, certificates are not accessible because they were encrypted.
         * (Integrity protection was also added, but is not checked here because null is
         * used as password)
         */
        keyStore.load(new ByteArrayInputStream(keyStoreData), null);
        System.out.println("Loading with `null`: Has entries: " + keyStore.aliases().hasMoreElements());
        
        /*
         * Keystore was actually stored with new char[0] as password.
         */
        keyStore.load(new ByteArrayInputStream(keyStoreData), new char[0]);
        System.out.println("Loading with `new char[0]`: Has entries: " + keyStore.aliases().hasMoreElements());
    }
    
    private static byte[] createKeyStoreData() {
        X509Certificate cert = createCert();
        
        try {
            KeyStore keyStore = KeyStore.getInstance("pkcs12");
            keyStore.load(null, null); // Initialize
            keyStore.setCertificateEntry("alias", cert);
            
            ByteArrayOutputStream out = new ByteArrayOutputStream();
            /*
             * Storing with null as integrity protection password. Therefore expecting
             * no integrity protection and unencrypted certificates.
             */
            keyStore.store(out, null);
            return out.toByteArray();
        }
        // None of these is possible
        catch (KeyStoreException | CertificateException | NoSuchAlgorithmException | IOException e) {
            throw new RuntimeException(e);
        }
    }
    
    private static X509Certificate createCert() {
        try {
            CertificateFactory factory = CertificateFactory.getInstance("X.509");
            ByteArrayInputStream in = new ByteArrayInputStream(CERT_PEM.getBytes(StandardCharsets.US_ASCII));
            return (X509Certificate) factory.generateCertificate(in);
        }
        // Certificate type is guaranteed to be supported and format is valid
        catch (CertificateException e) {
            throw new RuntimeException(e);
        }
    }
}

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FREQUENCY : always