RFR: 8358448: JFR: Incorrect time unit for MethodTiming event

[Erik Gahlin]

Could I have a review of a PR that fixes a regression introduced with [JDK-8047756](https://bugs.openjdk.org/projects/JDK/issues/JDK-8047756)?

The default unit for `@Timespan` in Java is nanos, but it should be set to ticks. Prior to JDK-8047756, annotations were taken from native code, so ticks were used.

Testing: 
100 * test/jdk//jdk/jfr/event/tracing/TestMethodTimingEvent.java on Windows, Linux and MacOS 
test/jdk//jdk/jfr/*

Thanks
Erik

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Commit messages:
 - Initial

Changes: https://git.openjdk.org/jdk/pull/25615/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=25615&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8358448
  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/25615.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/25615/head:pull/25615

PR: https://git.openjdk.org/jdk/pull/25615