test: Adapt threading tests to span streaming

[sentrivana]

The threading integration itself doesn't have any streaming branching, which is probably why these two threading tests that have to do with tracing got overlooked.

In streaming, the behavior in the propagate_scope=False case has changed -- all spans will be emitted. Previously, some of the spans wouldn't be emitted because they would be orphaned child spans.

[github-actions]

Codecov Results 📊

✅ 117082 passed | ⏭️ 5544 skipped | Total: 122626 | Pass Rate: 95.48% | Execution Time: 379m 19s

📊 Comparison with Base Branch

Metric	Change
Total Tests	📉 -14961
Passed Tests	📉 -13395
Failed Tests	—
Skipped Tests	📉 -1566

All tests are passing successfully.

✅ Patch coverage is 100.00%. Project has 2255 uncovered lines.
✅ Project coverage is 90.47%. Comparing base (base) to head (head).

Coverage diff

@@            Coverage Diff             @@
##          main       #PR       +/-##
==========================================
+ Coverage    90.24%    90.47%    +0.23%
==========================================
  Files          193       185        -8
  Lines        25707     23661     -2046
  Branches      9478      8680      -798
==========================================
+ Hits         23198     21406     -1792
- Misses        2509      2255      -254
- Partials      1436      1364       -72

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