Change ProcessTraceEvent.getDuration() to return long or Duration

**Describe the refactoring action**
Change ProcessTraceEvent.getDuration() to return long or Duration.

**Expected benefit**
Currently, it returns an int which might be truncated.

Start by locating ProcessTraceEvent.getDuration() and inspect its callers and related tests to understand the current duration unit and API expectations. Resolve whether the return type should be long or Duration, then update the affected usages and verify that durations are no longer truncated.

Written by the indexing model from the issue text.