RFR: 8317042: G1: Make TestG1ConcMarkStepDurationMillis use createTestJvm

[Leo Korinth]

On Wed, 27 Sep 2023 16:37:54 GMT, Leo Korinth <lkorinth at openjdk.org> wrote:

> Use createTestJvm.
> 
> Tested with: `-XX+UseG1GC` (pass 1), `-XX+UseZGC` (total 0), `-XX:G1ConcMarkStepDurationMillis=23` (total 0) and no options (pass 1)

Thanks Hamlin and Thomas!

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PR Comment: https://git.openjdk.org/jdk/pull/15948#issuecomment-1766267051