test: serve the whole-log fallback in the streamed log mocks

[vdusek]

Fixes a flaky test_actor_call_redirect_logs_to_default_logger_async[httpx2] (failed run).

When call() finishes before the log stream delivers its first chunk, StreamedLog reads the whole log with GET /log?raw=true (added in #1084). The mock_api and mock_api_failing_status_poll fixtures didn't serve that endpoint. In test_actor_call_returns_run_when_status_poll_fails_sync, the sync thread then retried the 500 with backoff, outlived the 5 s join in stop(), and logged its error into the next test's caplog on the same xdist worker.

Both fixtures now serve the whole log on that endpoint. Locally the failure went from 2/10 to 0/40 with the two tests in CI order, and test_logging.py under -n auto passed 30/30.

✍️ Drafted by Claude Code

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 95.46%. Comparing base (5f2b169) to head (4fb5116).
⚠️ Report is 2 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1114      +/-   ##
==========================================
- Coverage   95.50%   95.46%   -0.04%     
==========================================
  Files          61       61              
  Lines        5935     5935              
==========================================
- Hits         5668     5666       -2     
- Misses        267      269       +2     

Flag	Coverage Δ
integration	90.78% <ø> (-0.04%)	⬇️
unit	88.87% <ø> (-0.04%)	⬇️

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[Mantisus]

LGTM

[apify-approval-mirror]

Mirroring approval from @Mantisus.