RFR: JDK-8289524: Add JFR JIT restart event

[Matthias Baesken]

The JIT compiler restarts (see restart_compiler in NMethodSweeper::sweep_code_cache) would be a helpful addition to the JFR events. Currently we log the JIT stop operations in JFR (EventCodeCacheFull) but no restart.

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Commit messages:
 - JDK-8289524

Changes: https://git.openjdk.org/jdk/pull/9334/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=9334&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8289524
  Stats: 21 lines in 6 files changed: 20 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/9334.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/9334/head:pull/9334

PR: https://git.openjdk.org/jdk/pull/9334