[jdk21u] RFR: 8303815: Improve Metaspace test speed

[Thomas Stuefe]

Small improvement, low risk, that speeds up metaspace tests (jtreg and gtests).

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

Commit messages:
 - Backport de0e46c2f6dfa817bfa745195573810d250640de

Changes: https://git.openjdk.org/jdk21u/pull/98/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk21u&pr=98&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8303815
  Stats: 56 lines in 6 files changed: 34 ins; 5 del; 17 mod
  Patch: https://git.openjdk.org/jdk21u/pull/98.diff
  Fetch: git fetch https://git.openjdk.org/jdk21u.git pull/98/head:pull/98

PR: https://git.openjdk.org/jdk21u/pull/98