RFR: 8002277: Refactor two PBE classes to simplify maintenance

[Valerie Peng]

This change refactors the PBES2Core and PKCS12PBECipherCore classes in SunJCE provider as requested in the bug record. Functionality should remain the same with a clearer and simplified code/control flow with less lines of code.  This should improve readability and maintenance. I enhanced one existing regression test to test more scenarios. This test would pass before the proposed change and continues to pass with the proposed changes.

-------------

Commit messages:
 - Enhanced test with more decryption w/o parameters scenario.
 - 8002277: Refactor two PBE classes to simplify maintenance

Changes: https://git.openjdk.java.net/jdk/pull/8521/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=8521&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8002277
  Stats: 542 lines in 3 files changed: 168 ins; 289 del; 85 mod
  Patch: https://git.openjdk.java.net/jdk/pull/8521.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/8521/head:pull/8521

PR: https://git.openjdk.java.net/jdk/pull/8521