[jdk23] RFR: 8334421: assert(!oldbox->is_unbalanced()) failed: this should not be called for unbalanced region

[Vladimir Kozlov]

Clean backport of [JDK-8334421 fix](https://github.com/openjdk/jdk/commit/9c89f0861c1b6d25e1a7c3ac1add9a168d807788)

-------------

Commit messages:
 - Backport 9c89f0861c1b6d25e1a7c3ac1add9a168d807788

Changes: https://git.openjdk.org/jdk/pull/19931/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=19931&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8334421
  Stats: 237 lines in 6 files changed: 231 ins; 1 del; 5 mod
  Patch: https://git.openjdk.org/jdk/pull/19931.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/19931/head:pull/19931

PR: https://git.openjdk.org/jdk/pull/19931