fix: Set transaction source for unsampled streamed spans

[alexander-alderman-webb]

Description

Set the transaction source that is attached to events before the early return for NoOpStreamedSpan.

Enables creating a streaming lifecycle version of tests/integrations/django/test_basic.py::test_transaction_style.

Issues

Reminders

• Please add tests to validate your changes, and lint your code using tox -e linters.
• 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 📊

✅ 146 passed | Total: 146 | Pass Rate: 100% | Execution Time: 21.43s

All tests are passing successfully.

❌ Patch coverage is 0.00%. Project has 14324 uncovered lines.

Files with missing lines (1)

File	Patch %	Lines
scope.py	64.06%	⚠️ 322 Missing and 89 partials

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[alexander-alderman-webb]

I think the test is actually wrong, will update the test instead.