RFR: 8357470: src/java.base/share/classes/sun/security/util/Debug.java implement the test for args.toLowerCase

[Mikhail Yankelevich]

* added an automated mixed case option
* using multithreading now
* added logs for simpler debug
* added missing -Djava.security.auth.debug coverage

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Commit messages:
 - JDK-8357470: src/java.base/share/classes/sun/security/util/Debug.java implement the test for args.toLowerCase

Changes: https://git.openjdk.org/jdk/pull/25391/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=25391&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8357470
  Stats: 212 lines in 1 file changed: 130 ins; 4 del; 78 mod
  Patch: https://git.openjdk.org/jdk/pull/25391.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/25391/head:pull/25391

PR: https://git.openjdk.org/jdk/pull/25391