[jdk17u-dev] RFR: 8351997: AArch64: Interpreter volatile reference stores with G1 are not sequentially consistent

[Aleksey Shipilev]

Fixes AArch64 memory ordering problem. Readily manifests in new jcstress tests; there are sightings of related problems in JSR 133 tests. 

The patch is not clean, because [JDK-8301996](https://bugs.openjdk.org/browse/JDK-8301996) is in the way, and it is IMO too risky to backport. I picked up the JDK 21u backport version (https://git.openjdk.org/jdk21u-dev/commit/729f10053eab4b8fe8a857e14ce0f96a82c721b8), where I resolved some hunks to match the intended behavior, after checking `do_oop_store` clobbers the same `r3` as in mainline.

Additional testing:
 - [x] Linux AArch64 server release, jcstress `RefDekker` test now passes
 - [x] Linux AArch64 server release, jcstress `seqcst.volatiles.ref` tests now pass
 - [ ] Linux AArch64 server release, jcstress `all` tests now pass
 - [ ] Linux AArch64 server fastdebug, `all`

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Commit messages:
 - Backport 83b15da2eb3cb6c8937f517c9b75eaa9eeece314

Changes: https://git.openjdk.org/jdk17u-dev/pull/3697/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk17u-dev&pr=3697&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8351997
  Stats: 8 lines in 1 file changed: 4 ins; 0 del; 4 mod
  Patch: https://git.openjdk.org/jdk17u-dev/pull/3697.diff
  Fetch: git fetch https://git.openjdk.org/jdk17u-dev.git pull/3697/head:pull/3697

PR: https://git.openjdk.org/jdk17u-dev/pull/3697