RFR: 8376195: Convert ThreadLocalAllocBuffer to use Atomic<T> [v2]

[Thomas Schatzl]

> Hi all,
> 
>   please review the change to use `Atomic<T>` in `ThreadLocalAllocBuffer`.
> 
> Testing: gha
> 
> Thanks,
>   Thomas

Thomas Schatzl has updated the pull request incrementally with two additional commits since the last revision:

 - * kbarrett review
 - * kbarrett review

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/29386/files
  - new: https://git.openjdk.org/jdk/pull/29386/files/97f40d99..4fc931e7

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=29386&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=29386&range=00-01

  Stats: 28 lines in 4 files changed: 2 ins; 5 del; 21 mod
  Patch: https://git.openjdk.org/jdk/pull/29386.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/29386/head:pull/29386

PR: https://git.openjdk.org/jdk/pull/29386