RFR: 8324048: (fc) Make FileKey fields final

[Brian Burkhalter]

Replace use of IDs to set FileKey fields from native with passing down an array, at the expense of an array allocation.

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Commit messages:
 - 8324048: Replace SharedSecrets with fdval and handleval native functions
 - 8324048: Unix cleanup
 - 8324048: Windows implementation
 - 8324048: (fc) Make FileKey fields final

Changes: https://git.openjdk.org/jdk/pull/20429/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=20429&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8324048
  Stats: 78 lines in 4 files changed: 15 ins; 35 del; 28 mod
  Patch: https://git.openjdk.org/jdk/pull/20429.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/20429/head:pull/20429

PR: https://git.openjdk.org/jdk/pull/20429