[jdk11u-dev] RFR: 8227179: Test for new gc+metaspace=info output format

[Goetz Lindenmaier]

I backport this for parity with 11.0.18-oracle.
Requires a follow up.

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Commit messages:
 - Backport c0f6ce7c54e0e8266beb36de154f3c2e8747a24e

Changes: https://git.openjdk.org/jdk11u-dev/pull/1467/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk11u-dev&pr=1467&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8227179
  Stats: 135 lines in 1 file changed: 135 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk11u-dev/pull/1467.diff
  Fetch: git fetch https://git.openjdk.org/jdk11u-dev pull/1467/head:pull/1467

PR: https://git.openjdk.org/jdk11u-dev/pull/1467