RFR: 8357307: VM GC operations should have a public gc_succeeded()

[Thomas Schatzl]

Hi all,

   please review this cleanup that changes `VM_GC_Operation` to use `gc_succeeded` instead of `prologue_succeeded()`to indicate that a GC has been executed (once a GC is started, it will always finish, so the only reason that a VM op does not get executed is that we decide in the prologue that there has already been a GC).

After recent changes the change is/was mostly a renaming of the `prologue_succeeded`method - there is only one case for G1 where additional checks can cause no execution of the GC (e.g. because we started a low-priority concurrent mark and we are already currently marking. No point for doing a GC in that case).

Testing: tier1-4, gha

Thanks,
  Thomas

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Commit messages:
 - 8357307

Changes: https://git.openjdk.org/jdk/pull/25469/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=25469&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8357307
  Stats: 7 lines in 5 files changed: 0 ins; 2 del; 5 mod
  Patch: https://git.openjdk.org/jdk/pull/25469.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/25469/head:pull/25469

PR: https://git.openjdk.org/jdk/pull/25469