[jdk17u-dev] RFR: 8261495: Shenandoah: reconsider update references memory ordering

[Aleksey Shipilev]

Transplanted from https://github.com/openjdk/jdk17u/pull/254

Additional testing: 
 - [ ] Linux x86_64 fastdebug `hotspot_gc_shenandoah`
 - [ ] Linux x86_64 fastdebug `tier1` with Shenandoah
 - [ ] Linux AArch64 fastdebug `hotspot_gc_shenandoah`
 - [ ] Linux AArch64 fastdebug `tier1` with Shenandoah

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Commit messages:
 - Backport a96012a7afce6678125d3fb537f2433642953315

Changes: https://git.openjdk.java.net/jdk17u-dev/pull/8/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk17u-dev&pr=8&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8261495
  Stats: 130 lines in 7 files changed: 93 ins; 15 del; 22 mod
  Patch: https://git.openjdk.java.net/jdk17u-dev/pull/8.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk17u-dev pull/8/head:pull/8

PR: https://git.openjdk.java.net/jdk17u-dev/pull/8