RFR: 8359272: Several vmTestbase/compact tests timed out on large memory machine

[SendaoYan]

Hi all,

We observed 4 vmTestbase/vm/gc/compact tests run timed out on large physical memory machine (755G memory) with jtreg args `-timeoutFactor:4`. The other vmTestbase tests do not observed the same failure.
The tested class `vm.gc.compact.Compact` create lots objects util trigger OOM exception. But if the tested machine has very large physica memory, these tests need takes a lots of time to finish.
So this PR add jvm args `-Xmx3G` to make these tests will run finish in a deterministic time. Change has been verified locally, test-fix only, no risk.

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Commit messages:
 - 8359272: Several vmTestbase/compact tests timed out on large memory machine

Changes: https://git.openjdk.org/jdk/pull/25771/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=25771&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8359272
  Stats: 12 lines in 4 files changed: 8 ins; 0 del; 4 mod
  Patch: https://git.openjdk.org/jdk/pull/25771.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/25771/head:pull/25771

PR: https://git.openjdk.org/jdk/pull/25771