RFR: 8346920: Serial: Support allocation in old generation when heap is almost full

Thu Jan 23 15:17:27 UTC 2025

This PR restores the support for allocation in old-gen when heap is almost full, detected as non-empty young-gen after full gc, which was removed by mistake in [JDK-8333786](https://bugs.openjdk.org/browse/JDK-8333786). With this change, the benchmark attached to the ticket now completes in ~13 GC.

Test: tier1-5

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Commit messages:
 - sgc-alloc-in-old

Changes: https://git.openjdk.org/jdk/pull/23270/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=23270&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8346920
  Stats: 23 lines in 2 files changed: 22 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/23270.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/23270/head:pull/23270

PR: https://git.openjdk.org/jdk/pull/23270