RFR: 8317228: GC: Make TestXXXHeapSizeFlags use createTestJvm [v2]

[Leo Korinth]

On Fri, 13 Oct 2023 13:25:39 GMT, Stefan Johansson <sjohanss at openjdk.org> wrote:

>> I know of no colliding options ATM. They could be colliding in the future (especially if we chose to parse extra options not starting with a `-X`). Also, I think it is incredibly confusing to reuse the `vm.opt` namespace that is used by vanilla JTREG by our extension code in VMProps. I would object to put both in the `vm.opt` namespace.
>
> I agree it is a bit ugly and the point of this being an extension is good. An alternative would be to use `vm.xopt.Xmx` to even less clobber the `vm.opt` namespace, but I guess we already do by adding the `vm.opt.final` details. 
> 
> I'm ok with the current way, just wanted to raise possible alternatives.

`vm.xopt` was my first choice, but it works badly because of other reasons, so lets keep it as it is now.

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PR Review Comment: https://git.openjdk.org/jdk/pull/15986#discussion_r1358282079