RFR: 8356157: Remove retry loop in collect of SerialHeap and ParallelScavengeHeap

[Albert Mingkun Yang]

Simple removing unnecessary retrying logic because an gc-operation will run-to-completion, guaranteeing the increment of corresponding counters.

Test: tier1-3

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Commit messages:
 - remove-systemgc-loop

Changes: https://git.openjdk.org/jdk/pull/25032/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=25032&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8356157
  Stats: 33 lines in 2 files changed: 0 ins; 26 del; 7 mod
  Patch: https://git.openjdk.org/jdk/pull/25032.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/25032/head:pull/25032

PR: https://git.openjdk.org/jdk/pull/25032