[lworld] RFR: 8267710: Hook AlwaysAtomicAccesses to primitive classes atomicity rules

[Aleksey Shipilev]

`AlwaysAtomicAccesses` was added in JDK 9 to aid the research in the costs of requiring the always-atomic accesses. It would be nice to hook it up to current Valhalla code that handles explicitly declared atomic primitive classes.

Testing:
 - [x] ad-hoc jcstress tests with lworld and `-XX:(-|+)AlwaysAtomicAccesses`

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

Commit messages:
 - 8267710: Hook AlwaysAtomicAccesses to primitive classes atomicity rules

Changes: https://git.openjdk.java.net/valhalla/pull/427/files
 Webrev: https://webrevs.openjdk.java.net/?repo=valhalla&pr=427&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8267710
  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/valhalla/pull/427.diff
  Fetch: git fetch https://git.openjdk.java.net/valhalla pull/427/head:pull/427

PR: https://git.openjdk.java.net/valhalla/pull/427