[jdk16] RFR: 8258915: More temporary buffer cleanup

[Weijun Wang]

More temporary byte array, char array, keyspec cleanup around keys and passwords.

No new regression test.

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Commit messages:
 - 8258915: More temporary buffer cleanup

Changes: https://git.openjdk.java.net/jdk16/pull/98/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk16&pr=98&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8258915
  Stats: 1544 lines in 51 files changed: 704 ins; 428 del; 412 mod
  Patch: https://git.openjdk.java.net/jdk16/pull/98.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk16 pull/98/head:pull/98

PR: https://git.openjdk.java.net/jdk16/pull/98