RFR: 8302883: JFR: Improve periodic events [v2]

[Erik Gahlin]

> Could I have a review of an enhancement that addresses shortcomings of the RequestEngine class when it comes to maintainability, thread safety, scalability and predictability. See bug for details.
> 
> Testing:
> 100 * jdk/jdk/jfr
> Manual inspection of periodic events to make sure they are emitted as expected.
> 
> Thanks
> Erik

Erik Gahlin has updated the pull request incrementally with one additional commit since the last revision:

  Remove increment

-------------

Changes:
  - all: https://git.openjdk.org/jdk/pull/12668/files
  - new: https://git.openjdk.org/jdk/pull/12668/files/140f87e5..11ae47e7

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=12668&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=12668&range=00-01

  Stats: 26 lines in 3 files changed: 16 ins; 7 del; 3 mod
  Patch: https://git.openjdk.org/jdk/pull/12668.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/12668/head:pull/12668

PR: https://git.openjdk.org/jdk/pull/12668