RFR: 8370082: Intermediate objects clean up in DHKEM and HKDF

[Weijun Wang]

Clean up more intermediate objects created during HKDF and DHKEM operations.

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Commit messages:
 - more clean up

Changes: https://git.openjdk.org/jdk/pull/27921/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=27921&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8370082
  Stats: 32 lines in 5 files changed: 25 ins; 0 del; 7 mod
  Patch: https://git.openjdk.org/jdk/pull/27921.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/27921/head:pull/27921

PR: https://git.openjdk.org/jdk/pull/27921