MID-11073 Fix threshold suspension in iterative scripting

[kay1313]

Summary

Fixes MID-11073, where iterative scripting tasks did not suspend correctly when a threshold policy action was triggered from inside a script.

---

Problem

When an iterative script called a model operation such as midpoint.modifyObject(delta), a ThresholdPolicyViolationException could be wrapped by the script evaluation layer as an ExpressionEvaluationException.

Because error categorization checked only the top-level exception, the task treated the threshold violation as a normal script/item failure. The task then continued processing remaining objects and eventually finished as Closed/Error instead of stopping as Suspended.

---

Fix

Detect ThresholdPolicyViolationException in the exception cause chain, so wrapped threshold violations are still categorized as POLICY_THRESHOLD.

---

Test

Added an integration test for an iterative scripting task with:

• 10 test users
• threshold count 3
• policy action suspendTask

The test verifies that the task suspends after the threshold is reached, with 2 successful items and 1 threshold-triggering failure.