RFR: 8314935: Shenandoah: Unable to throw OOME on back-to-back Full GCs

[William Kemper]

Retry allocations until at least one full gc is complete, do not spin unnecessarily when gc is not making progress.

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Commit messages:
 - Retry allocations until at least one full gc is complete

Changes: https://git.openjdk.org/jdk/pull/15500/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=15500&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8314935
  Stats: 22 lines in 2 files changed: 5 ins; 11 del; 6 mod
  Patch: https://git.openjdk.org/jdk/pull/15500.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/15500/head:pull/15500

PR: https://git.openjdk.org/jdk/pull/15500