Add support for Oracle Database 21c

Is your feature request related to a problem? Please describe.

I cannot install utPLSQL in the in Oracle Database 21c, because the package DBMS_OBFUSCATION_TOOLKIT is not available anymore.

Describe the solution you'd like

Use an alternative solution for DBMS_OBFUSCATION_TOOLKIT. This package was desupported in 10gR2 and is not installed anymore. See https://docs.oracle.com/en/database/oracle/oracle-database/21/arpls/release-changes.html#GUID-6607028A-4813-400B-8C7A-B2BAD892842B . DBMS_CRYPTO could be an alternative as described in the docs.