RFR: 8302215: G1: Last-ditch Full GC should do serial compaction for tail regions in per thread compaction points.

[Ivan Walulya]

Hi all, 

Please review this change to call `G1FullCollector::phase2c_prepare_serial_compaction` when `do_maximal_compaction`. For maximum compaction, we re-prepare all objects in the "tail" regions of the per thread compaction points.

Testing: Tier 1-3.

Thanks

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Commit messages:
 - Thomas suggestions
 - copyright years
 - initial

Changes: https://git.openjdk.org/jdk/pull/12529/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=12529&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8302215
  Stats: 103 lines in 8 files changed: 78 ins; 0 del; 25 mod
  Patch: https://git.openjdk.org/jdk/pull/12529.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/12529/head:pull/12529

PR: https://git.openjdk.org/jdk/pull/12529