fix iterator: set omp to 1

[alwayslove2013]

Use search_pool to handle iterator's next_batch instead of init

[mergify]

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[alwayslove2013]

/kind improvement

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 73.84%. Comparing base (3c46f4c) to head (64010b8).
Report is 279 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff            @@
##           main     #989       +/-   ##
=========================================
+ Coverage      0   73.84%   +73.84%     
=========================================
  Files         0       82       +82     
  Lines         0     6916     +6916     
=========================================
+ Hits          0     5107     +5107     
- Misses        0     1809     +1809     

see 82 files with indirect coverage changes

[cqy123456]

/lgtm

[cydrain]

Generally e2e should finish in 30 minutes.
Comparing a success e2e run with yours

success e2e run:
[2024-12-17 04:35:58 - INFO - test_func.py:48]: Start building index, index_type = HNSW, metric_type = L2
[2024-12-17 04:36:00 - INFO - test_func.py:39]: ### check_build_index runtime: 2.301s
[2024-12-17 04:36:00 - INFO - test_func.py:39]: ### iterator_search runtime: 0.023s
[2024-12-17 04:36:00 - INFO - test_func.py:39]: ### iterator_search runtime: 0.055s
[2024-12-17 04:36:01 - INFO - test_func.py:39]: ### iterator_search runtime: 0.219s

yours:
[2024-12-17 06:58:15 - INFO - test_func.py:48]: Start building index, index_type = HNSW, metric_type = L2
[2024-12-17 06:58:17 - INFO - test_func.py:39]: ### check_build_index runtime: 2.460s

I cannot see "iterator_search runtime" in your e2e log, there must be something wrong

[cqy123456]

Deadlock caused by nested calls to search thread pool.
We can let iterator workspace hold a shared_ptr of search thread pool, and generate thread tasks itself.
@alwayslove2013

[sre-ci-robot]

New changes are detected. LGTM label has been removed.

[sre-ci-robot]

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[alwayslove2013]

/hold

[alexanderguzhva]

@alwayslove2013 is it good to review this PR? thanks

[alwayslove2013]

@alexanderguzhva Sorry, there are still some compatibility issues with bruteforce-iterator. I will fix it asap. please hold~