RFR: JDK-8289798: Update to use jtreg 7 [v6]

[Thomas Stuefe]

On Mon, 5 Sep 2022 07:18:09 GMT, Christian Stein <cstein at openjdk.org> wrote:

> > Is jtreg 7 downward compatible? Can I use it to test older JDKs, if yes, down to which version?
> 
> Yes, down to JDK 11.
> 
> Quote from [Coming soon: jtreg 7](https://mail.openjdk.org/pipermail/jdk-dev/2022-August/006869.html)
> 
> > Also starting with version 7, jtreg is compiled with JDK 11 and so requires a recent release of JDK 11 to run it.

I read this to mean JT_JAVA, so the JVM running jtreg, not the testee VM.

But you are saying that the testee VM (`-jdk` option) can be JDK11 or later? I wonder whether I can use jtreg7 to test downport JDKs, especially since you wrote 

"This did affect some existing JDK tests, but those tests that
relied on specific jar file names have already been updated."

So I guess at the minimum we would have to downport those test changes to be able to test older JDKs with the new jtreg, right?

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PR: https://git.openjdk.org/jdk/pull/9393