Hardcoded credentials

Apache Kylin provides encryption classes PasswordPlaceholderConfigurer to help users encrypt their passwords. In the encryption algorithm used by this encryption class, the cipher is initialized with a hardcoded key and IV. If users use class PasswordPlaceholderConfigurer to encrypt their password and configure it into kylin's configuration file, there is a risk that the password may be decrypted. This issue affects Apache Kylin 2 version 2.6.6 and prior versions; Apache Kylin 3 version 3.1.2 and prior versions; Apache Kylin 4 version 4.0.0 and prior versions.