[jdk25u] RFR: 8361520: Stabilize SystemGC benchmarks

[KavyaKS94]

Clean backport. tested locally by running `sudo make test TEST="micro:vm.gc.systemgc"`


Benchmark                       Mode  Cnt    Score   Error  Units
AllDead.gc                        ss  125   12.133 ± 1.641  ms/op
AllLive.gc                        ss  125   44.718 ± 1.723  ms/op
DifferentObjectSizesArray.gc      ss  125   78.024 ± 5.487  ms/op
DifferentObjectSizesHashMap.gc    ss  125   90.232 ± 3.675  ms/op
DifferentObjectSizesTreeMap.gc    ss  125  105.918 ± 3.267  ms/op
HalfDeadFirstPart.gc              ss  125   27.406 ± 0.601  ms/op
HalfDeadInterleaved.gc            ss  125   88.963 ± 0.827  ms/op
HalfDeadInterleavedChunks.gc      ss  125   74.533 ± 3.662  ms/op
HalfDeadSecondPart.gc             ss  125   27.213 ± 0.452  ms/op
HalfHashedHalfDead.gc             ss  125   95.042 ± 1.031  ms/op
NoObjects.gc                      ss  125    9.586 ± 0.327  ms/op
OneBigObject.gc                   ss  125   74.786 ± 2.621  ms/op
Finished running test 'micro:vm.gc.systemgc'
Test report is stored in /Users/kavyaks/jdk25u-cpu/build/macosx-x64/test-results/micro_vm_gc_systemgc
==============================
Test summary
==============================
   TEST                                              TOTAL  PASS  FAIL ERROR  SKIP
   micro:vm.gc.systemgc                                  1     1     0     0     0
==============================
TEST SUCCESS

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

Commit messages:
 - 8361520: Stabilize SystemGC benchmarks

Changes: https://git.openjdk.org/jdk25u/pull/237/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk25u&pr=237&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8361520
  Stats: 125 lines in 12 files changed: 125 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk25u/pull/237.diff
  Fetch: git fetch https://git.openjdk.org/jdk25u.git pull/237/head:pull/237

PR: https://git.openjdk.org/jdk25u/pull/237