RFR: JDK-8303815: Improve Metaspace test speed

[Stefan Karlsson]

On Thu, 17 Aug 2023 07:31:11 GMT, Thomas Stuefe <stuefe at openjdk.org> wrote:

> Small adjustments that cut down time needed for Metaspace tests:
> 
> gtests: 22 seconds -> 6 seconds
> elastic metaspace jtreg tests: 36 seconds -> 15 seconds
> 
> For the jtreg tests, I preserve the option to execute them full time as manual tests

Marked as reviewed by stefank (Reviewer).

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PR Review: https://git.openjdk.org/jdk/pull/15324#pullrequestreview-1591098519