[Caideyipi]

Description

Follow-up to #18338.

• Initialize workerThreads once as a final CopyOnWriteArrayList instead of publishing a mutable collection through a volatile reference.
• Clear and repopulate the list during initialization.
• Keep procedure metrics safe before and during ConfigNode leader initialization.

Tests

• mvn -pl iotdb-core/confignode -Dtest=TestProcedureExecutor -Ddevelocity.off=true test (9 tests)
• Checkstyle and Spotless checks included in the Maven run
• git diff --check

[Caideyipi]

Self-review passed. I reviewed the full PR diff and the relevant ProcedureExecutor lifecycle; no actionable issues were found, so no code fixes were needed.

I merged the latest master into the PR branch in commit 58fc48317c3 and pushed it. Local validation passed: TestProcedureExecutor (9 tests), Checkstyle, and Spotless. The earlier Windows DataNode unit-test failure is outside this ConfigNode change; CI has restarted for the updated head.