RFR: Merge jdk19

[David Holmes]

Forward port JDK 19 -> JDK 20

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Commit messages:
 - Merge remote-tracking branch 'jdk19/master' into Merge_jdk19
 - 8291524: jdk/jfr/event/runtime/TestClassLoaderStatsEvent.java Value not equal to 2, field='hiddenClassCount', value='0'
 - 8291512: Snippetize modules API examples

The webrevs contain the adjustments done while merging with regards to each parent branch:
 - master: https://webrevs.openjdk.org/?repo=jdk&pr=9720&range=00.0
 - jdk19: https://webrevs.openjdk.org/?repo=jdk&pr=9720&range=00.1

Changes: https://git.openjdk.org/jdk/pull/9720/files
  Stats: 33 lines in 6 files changed: 6 ins; 9 del; 18 mod
  Patch: https://git.openjdk.org/jdk/pull/9720.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/9720/head:pull/9720

PR: https://git.openjdk.org/jdk/pull/9720