RFR: 8002277: Refactor two PBE classes to simplify maintenance [v8]

[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.

Valerie Peng has updated the pull request incrementally with one additional commit since the last revision:

  reset ivSpec and minor nit fix.

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Changes:
  - all: https://git.openjdk.java.net/jdk/pull/8521/files
  - new: https://git.openjdk.java.net/jdk/pull/8521/files/c1893f8b..95dfa948

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=8521&range=07
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=8521&range=06-07

  Stats: 8 lines in 1 file changed: 1 ins; 2 del; 5 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