RFR: 8266936: Add a finalization JFR event [v2]

[Brent Christian]

> Please review this enhancement to add a new JFR event, generated whenever a finalizer is run.
> (The makeup is similar to the Deserialization event, [JDK-8261160](https://bugs.openjdk.java.net/browse/JDK-8261160).)
> 
> The event's only datum (beyond those common to all jfr events) is the class of the object that was finalized.
> 
> The Category for the event:
> `"Java Virtual Machine" / "GC" / "Finalization"`
> is what made sense to me, even though the event is generated from library code.
> 
> Along with the new regtest, I added a run mode to the basic finalizer test to enable jfr.
> Automated testing looks good so far.
> 
> Thanks,
> -Brent

Brent Christian has updated the pull request incrementally with one additional commit since the last revision:

  Test flag should be volatile

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

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/4101/files
  - new: https://git.openjdk.java.net/jdk/pull/4101/files/200268ab..e0ef383b

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=4101&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=4101&range=00-01

  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk/pull/4101.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/4101/head:pull/4101

PR: https://git.openjdk.java.net/jdk/pull/4101