RFR: 8332082: Shenandoah: Use consistent tests to determine when pre-write barrier is active [v3]

[William Kemper]

> This is consistent with c1 and other platforms.

William Kemper has updated the pull request incrementally with one additional commit since the last revision:

  Fix typo

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Changes:
  - all: https://git.openjdk.org/jdk/pull/19180/files
  - new: https://git.openjdk.org/jdk/pull/19180/files/3271fecf..cff7dc0c

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=19180&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=19180&range=01-02

  Stats: 3 lines in 1 file changed: 0 ins; 0 del; 3 mod
  Patch: https://git.openjdk.org/jdk/pull/19180.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/19180/head:pull/19180

PR: https://git.openjdk.org/jdk/pull/19180