RFR: 8316992: 2 Null pointer dereference defect groups in atomic.hpp:616

[Doug Simon]

Refactors some JVMCI C++ code that leads a static analysis tool to think a nullptr can be passed to [`Atomic::PlatformStore<4ull>::operator()<int>`](https://github.com/openjdk/jdk/blob/b75c134facc4dbd9f171024a12994dda818c5471/src/hotspot/share/runtime/atomic.hpp#L616-L624).

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Commit messages:
 - remove use of get_current_thread helper which can mislead static code analysis tools

Changes: https://git.openjdk.org/jdk/pull/17676/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=17676&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8316992
  Stats: 13 lines in 1 file changed: 0 ins; 9 del; 4 mod
  Patch: https://git.openjdk.org/jdk/pull/17676.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/17676/head:pull/17676

PR: https://git.openjdk.org/jdk/pull/17676