RFR: 8365780: G1: Remset for young regions are cleared too early during Full GC

[Ivan Walulya]

Hi,
Please review this patch to move clearing of the young region remsets to later in the Full GC. G1HeapVerifier specifically G1FullCollector::verify_after_marking still assumes that the remsets for young regions are still valid and with status complete. Clearing these remsets too early triggers the verification failure.

Testing: - Tiers 1-3

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Commit messages:
 - can be later
 - space
 - reset remset clearing

Changes: https://git.openjdk.org/jdk/pull/26839/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=26839&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8365780
  Stats: 7 lines in 2 files changed: 5 ins; 2 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/26839.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/26839/head:pull/26839

PR: https://git.openjdk.org/jdk/pull/26839