RFR: JDK-8297959: Provide better descriptions for some Operating System JFR events

[Matthias Baesken]

Some Operating System JFR events currently lack descriptions , this could be improved.
See for example https://sap.github.io/SapMachine/jfrevents/20.html#osinformation

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Commit messages:
 - JDK-8297959

Changes: https://git.openjdk.org/jdk/pull/11478/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=11478&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8297959
  Stats: 9 lines in 1 file changed: 6 ins; 0 del; 3 mod
  Patch: https://git.openjdk.org/jdk/pull/11478.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/11478/head:pull/11478

PR: https://git.openjdk.org/jdk/pull/11478