tests: Move streaming decorator tests

[sentrivana]

Description

Moving streaming @trace decorator tests from test_span_streaming to test_decorator and adapting existing tests to also test the streamed variant if applicable.

Issues

• Part of Run non-integration tests on span first #5395

Reminders

• Please add tests to validate your changes, and lint your code using uv run ruff.
• Add GH Issue ID & Linear ID (if applicable)
• PR title should use conventional commit style (feat:, fix:, ref:, meta:)
• For external contributors: CONTRIBUTING.md, Sentry SDK development docs, Discord community

[github-actions]

Codecov Results 📊

✅ 89922 passed | ⏭️ 6288 skipped | Total: 96210 | Pass Rate: 93.46% | Execution Time: 311m 43s

📊 Comparison with Base Branch

Metric	Change
Total Tests	📈 +71
Passed Tests	📈 +80
Failed Tests	—
Skipped Tests	📉 -9

All tests are passing successfully.

✅ Patch coverage is 100.00%. Project has 2435 uncovered lines.
✅ Project coverage is 89.77%. Comparing base (base) to head (head).

Coverage diff

@@            Coverage Diff             @@
##          main       #PR       +/-##
==========================================
+ Coverage    89.74%    89.77%    +0.03%
==========================================
  Files          192       192         —
  Lines        23809     23809         —
  Branches      8218      8218         —
==========================================
+ Hits         21367     21374        +7
- Misses        2442      2435        -7
- Partials      1347      1347         —

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