RFR: 8357797: Use StructuredTaskScopeImpl.ST_NEW for state init

[Aleksey Shipilev]

SonarCloud complains `ST_NEW` constant is not used. Looks to me the constructor implicitly relies on default value for `state`. It would be cleaner to initialize it explicitly

Additional testing:
 - [x] Linux x86_64 server fastdebug, `java/util/concurrent`

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

Commit messages:
 - Fix

Changes: https://git.openjdk.org/jdk/pull/25452/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=25452&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8357797
  Stats: 1 line in 1 file changed: 1 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/25452.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/25452/head:pull/25452

PR: https://git.openjdk.org/jdk/pull/25452