RFR: 8372650: Convert GenericWaitBarrier to use Atomic<T> [v2]

[Kim Barrett]

> Please review this change to GenericWaitBarrier to use Atomic rather than
> directly applying AtomicAccess to volatile members.
> 
> Testing: mach5 tier1-5

Kim Barrett has updated the pull request incrementally with one additional commit since the last revision:

  undo unintended load_acquire

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/28527/files
  - new: https://git.openjdk.org/jdk/pull/28527/files/618e1a03..3577ba5e

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=28527&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=28527&range=00-01

  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/28527.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/28527/head:pull/28527

PR: https://git.openjdk.org/jdk/pull/28527