chore(fastapi): Drop transactions

[sentrivana]

Description

Also converted tests that were assuming trace_lifecycle="static", and dropped transaction-specific tests that are not transferable to span streaming.

Issues

Closes https://linear.app/getsentry/issue/PY-2692/remove-transaction-based-tracing-from-fastapi

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

[linear-code]

PY-2692

[github-actions]

Codecov Results 📊

✅ 117314 passed | ⏭️ 5560 skipped | Total: 122874 | Pass Rate: 95.48% | Execution Time: 393m 21s

📊 Comparison with Base Branch

Metric	Change
Total Tests	📉 -2948
Passed Tests	📉 -1746
Failed Tests	—
Skipped Tests	📉 -1202

All tests are passing successfully.

✅ Patch coverage is 100.00%. Project has 2256 uncovered lines.
✅ Project coverage is 90.45%. Comparing base (base) to head (head).

Files with missing lines (1)

File	Patch %	Lines
sentry_sdk/integrations/fastapi.py	100.00%	⚠️ 1 partials

Coverage diff

@@            Coverage Diff             @@
##          main       #PR       +/-##
==========================================
+ Coverage    90.23%    90.45%    +0.22%
==========================================
  Files          193       185        -8
  Lines        25667     23628     -2039
  Branches      9462      8674      -788
==========================================
+ Hits         23160     21372     -1788
- Misses        2507      2256      -251
- Partials      1444      1369       -75

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