Fix thread unwind in CallStack.

The CallStack unwind of a different thread was broken since it
wasn't properly setting the tid value.

Fix this problem and add new unit tests to verify the behavior.

Bug: 246405269

Test: New unit tests pass.
Test: Ran unit tests for 1000 operations to verify not flaky.
Change-Id: I00342e6cdcdb4bcb68f29734dadee6c987c98040