test: make org.jbpm.executor.impl.jms.JmsAvaiableJobExecutorTest deterministic

[Jack-LuoHongyi]

Summary

• Type: concurrency-safe collection (listener recording)
• Scope: test-only; no production changes
• Module: jbpm-services/jbpm-executor
• Test: org.jbpm.executor.impl.jms.JmsAvaiableJobExecutorTest#testAsyncAuditProducerPrioritizedJobs

Root Cause
The test records executed job keys from asynchronous callbacks into a shared list. The original list was not thread-safe, while callbacks may run on different threads, which can lead to occasional missed entries during concurrent writes.

Fix
Replace the list used to record executed job keys with a thread-safe collection (CopyOnWriteArrayList). This preserves the original assertions and intent — verifying that both "high priority" and "low priority" jobs are executed — without relaxing the checks.

Validation

• Local execution passes consistently.
• Additional stability validation performed using the Maven plugin edu.illinois:nondex-maven-plugin:2.1.7 with multiple runs.
• Scope remains test-only; no production code is touched.

Risk
Low. The change is limited to test code and uses a standard JDK concurrency-safe collection. Assertions remain unchanged and continue to validate the same behavior.