RFR: 8348400: GenShen: assert(ShenandoahHeap::heap()->is_full_gc_in_progress() || (used_regions_size() <= _max_capacity)) failed: Cannot use more than capacity #

[William Kemper]

When the capacity of a trashed region is transferred from the young to old generation, we must first recycle the region to break its affiliation with the young generation. Failing to do this may violate the constraint that the capacity of a generation is always equal to or greater than the capacity of its affiliated regions.

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Commit messages:
 - Recycle young trash region before flipping to GC

Changes: https://git.openjdk.org/jdk/pull/23282/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=23282&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8348400
  Stats: 21 lines in 2 files changed: 11 ins; 0 del; 10 mod
  Patch: https://git.openjdk.org/jdk/pull/23282.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/23282/head:pull/23282

PR: https://git.openjdk.org/jdk/pull/23282