[jdk21u-dev] RFR: 8321122: Shenandoah: Remove ShenandoahLoopOptsAfterExpansion flag

[Aleksey Shipilev]

Clean backport to improve Shenandoah maintainability. 

Additional testing:
 - [x] macos-aarch64-server-fastdebug, `hotspot_gc_shenandoah`

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Commit messages:
 - Backport b02fc8681e57d75b5e05ce98216c53ff4d1e3b5d

Changes: https://git.openjdk.org/jdk21u-dev/pull/178/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk21u-dev&pr=178&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8321122
  Stats: 18 lines in 2 files changed: 5 ins; 11 del; 2 mod
  Patch: https://git.openjdk.org/jdk21u-dev/pull/178.diff
  Fetch: git fetch https://git.openjdk.org/jdk21u-dev.git pull/178/head:pull/178

PR: https://git.openjdk.org/jdk21u-dev/pull/178