RFR: 8292266: Add JFR event for total Reference processing time [v5]

[Sangheon Kim]

> Hi all,
> 
> Can I have reviews for this change that adds a new JFR event for total Reference Processing time?
> 
> The goal is to generate a new JFR event if there is already measured time. This CR doesn't add new time measurement.
> 
> Testing: hs-tier1 ~ 3
> 
> Thanks,
> Sangheon

Sangheon Kim has updated the pull request incrementally with two additional commits since the last revision:

 - Add Shenandoah and Z. albertnetymk and egahlin comment.
 - Revert to initial commit. Albert review.

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/11230/files
  - new: https://git.openjdk.org/jdk/pull/11230/files/2b119e74..2faec9e3

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=11230&range=04
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=11230&range=03-04

  Stats: 52 lines in 15 files changed: 23 ins; 20 del; 9 mod
  Patch: https://git.openjdk.org/jdk/pull/11230.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/11230/head:pull/11230

PR: https://git.openjdk.org/jdk/pull/11230