RFR: 8361639: JFR: Incorrect top frame for I/O events

[Erik Gahlin]

Could I have a review of the change that ensures that the top frame for I/O events is not an internal JDK method, such as FileReadEvent::offer? This change is dependent on [JDK-8361640](https://bugs.openjdk.org/browse/JDK-8361640).

Testing: tier1, tier2 + jdk/jdk/jfr

Thanks
Erik

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Commit messages:
 - Cleanup and socket adapters
 - Use switch expression
 - Revert accidental move
 - Fix whitespace
 - Initial

Changes: https://git.openjdk.org/jdk/pull/26211/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=26211&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8361639
  Stats: 375 lines in 6 files changed: 358 ins; 12 del; 5 mod
  Patch: https://git.openjdk.org/jdk/pull/26211.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/26211/head:pull/26211

PR: https://git.openjdk.org/jdk/pull/26211