RFR: 8354949: JFR: Split up the EventInstrumentation class

[Erik Gahlin]

Could I have a review of a PR that cleans up the EventInstrumentation class and moves the non-modifying parts into a separate class (ClassInspector)? 

I deleted the code that removes the instrumentation (buildUninstrumented), because it has never been used. If there should be a need for it in the future, it's not hard to add code that inserts empty method bodies.

Testing: tier1 + jdk/jdk/jfr/test

Thanks
Erik

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Commit messages:
 - Initial

Changes: https://git.openjdk.org/jdk/pull/24726/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=24726&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8354949
  Stats: 977 lines in 5 files changed: 448 ins; 359 del; 170 mod
  Patch: https://git.openjdk.org/jdk/pull/24726.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/24726/head:pull/24726

PR: https://git.openjdk.org/jdk/pull/24726