test: poll for task runs to fix flaky integration tests

[vdusek]

test_task_runs failed on master (run 38285189656) with assert 0 >= 1: the task's run list was empty right after call() returned. The run listing is eventually consistent, so a read straight after the run finishes can miss it. The JS client hit the same flake in apify/apify-client-js#1136.

Both test_task_runs and test_task_last_run now poll with poll_until_condition until the API returns the run that call() started. test_task_runs also checks for that run's id instead of just a non-empty page.

✍️ Drafted by Claude Code

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 95.46%. Comparing base (7fec14a) to head (34738bc).
⚠️ Report is 3 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #1123   +/-   ##
=======================================
  Coverage   95.46%   95.46%           
=======================================
  Files          61       61           
  Lines        5935     5935           
=======================================
  Hits         5666     5666           
  Misses        269      269           

Flag	Coverage Δ
integration	90.58% <ø> (-0.02%)	⬇️
unit	88.87% <ø> (ø)

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[Mantisus]

LGTM

[apify-approval-mirror]

Mirroring approval from @Mantisus.