RFR: 8356698: JFR: @Contextual

[Erik Gahlin]

Could I have a review of a new annotation that can be used to annotate a field as contextual. 

Testing: jdk/jdk/jfr + tier1

Thanks
Erik

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Commit messages:
 - Simplification and cleanup
 - Merge
 - Remove mistakenly added file
 - Update
 - Whitspace
 - Initial

Changes: https://git.openjdk.org/jdk/pull/25249/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=25249&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8356698
  Stats: 706 lines in 6 files changed: 698 ins; 3 del; 5 mod
  Patch: https://git.openjdk.org/jdk/pull/25249.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/25249/head:pull/25249

PR: https://git.openjdk.org/jdk/pull/25249