feat(langchain): Support span streaming

[alexander-alderman-webb]

Note: Depends on #6407

Description

Use sentry_sdk.traces.start_span and replace Span.set_data() with StreamedSpan.set_attribute() when in span streaming mode.

Also port the patch for Pregel.invoke() used by create_agent() in the LangChain test suite.

Parametrize tests on the trace lifecycle option.

Issues

Closes #6031

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 📊

✅ 282 passed | Total: 282 | Pass Rate: 100% | Execution Time: 44.73s

All tests are passing successfully.

❌ Patch coverage is 2.27%. Project has 14841 uncovered lines.

Files with missing lines (2)

File	Patch %	Lines
langchain.py	3.00%	⚠️ 614 Missing
langgraph.py	5.58%	⚠️ 237 Missing

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