RFR: 8358594: Misleading keyLength value captured in JFR event for ML-KEM key [v4]

[Weijun Wang]

> Add more comment on why `KeyUtil::getKeySize` could return -1. Add a new method `getNistCategory` to get the NIST security category.

Weijun Wang has updated the pull request incrementally with two additional commits since the last revision:

 - enhance test
 - a doc fix elsewhere

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/25642/files
  - new: https://git.openjdk.org/jdk/pull/25642/files/5ec95fb2..9e1a257c

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=25642&range=03
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=25642&range=02-03

  Stats: 11 lines in 2 files changed: 9 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/25642.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/25642/head:pull/25642

PR: https://git.openjdk.org/jdk/pull/25642