fix: eagerly update local head on forefront ops in shared RequestQueue

[vdusek]

Summary

The shared RequestQueue client relied on list_and_lock_head to reflect forefront updates from update_request(forefront=true) and batch_add_requests(forefront=true). Because the Apify API has a propagation delay between those operations and list_and_lock_head (#808), the next fetch could return a stale request — the failing CI for test_request_reclaim_with_forefront[shared] returned https://example.com/2 instead of the just-reclaimed /1.

This mirrors the single-mode client (_request_queue_single_client.py:262) by eagerly updating the local _queue_head deque on forefront operations:

• reclaim_request(forefront=True) — appendleft the reclaimed request_id (with contextlib.suppress(ValueError) dedupe). Removed the now-redundant _should_check_for_forefront_requests = True flag setting.
• add_batch_of_requests(forefront=True) — appendleft newly-added (non-unprocessed) request IDs in reverse order so the first batched item ends up at the front. Also passed hydrated_request=request to _cache_request so subsequent fetches don't need an extra API roundtrip.
• Removed _should_check_for_forefront_requests entirely (and its leftover-buffer logic in _list_head). With eager local updates the cache is authoritative for our own forefront ops; natural drain (len(_queue_head) ≤ 1) handles the refresh for picking up other clients' changes.

The motivation for the change is to fix this flaky test in CI: https://github.com/apify/apify-sdk-python/actions/runs/25316848848/job/74216228877

[codecov]

Codecov Report

❌ Patch coverage is 7.14286% with 13 lines in your changes missing coverage. Please review.
✅ Project coverage is 75.74%. Comparing base (6f82da9) to head (73a6568).
⚠️ Report is 2 commits behind head on master.

Files with missing lines	Patch %	Lines
...age_clients/_apify/_request_queue_shared_client.py	7.14%	13 Missing ⚠️

❗ There is a different number of reports uploaded between BASE (6f82da9) and HEAD (73a6568). Click for more details.

HEAD has 1 upload less than BASE

Flag	BASE (6f82da9)	HEAD (73a6568)
integration	1	0

Additional details and impacted files

@@             Coverage Diff             @@
##           master     #887       +/-   ##
===========================================
- Coverage   86.94%   75.74%   -11.21%     
===========================================
  Files          48       48               
  Lines        2942     2944        +2     
===========================================
- Hits         2558     2230      -328     
- Misses        384      714      +330     

Flag	Coverage Δ
e2e	37.73% <7.14%> (+<0.01%)	⬆️
integration	?
unit	75.74% <7.14%> (+0.05%)	⬆️

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