refactor: consolidate duplicated array element type mapping

[pymilvus-bot]

Summary

The DataType-to-protobuf-attribute mapping for array elements (e.g.
INT64 -> long_data, VARCHAR -> string_data) was copy-pasted across
four separate functions in entity_helper.py and search_result.py.

This PR introduces a single _ARRAY_ELEMENT_TYPE_TO_ATTR dict and
rewrites the helpers to use it:

• Merge extract_array_row_data_with_validity / _no_validity into one
  extract_array_rows(field_data, rows, count, has_valid) function
• Simplify extract_array_row_data (single-row variant) to a two-line
  dict lookup
• Simplify extract_array_row_data in search_result.py to use the
  shared mapping

Net result: -86 lines, one source of truth for the mapping, easier
to maintain when new array element types are added.

Signed-off-by: pymilvus-bot pymilvus@zilliz.com

[codecov]

Codecov Report

❌ Patch coverage is 94.44444% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 90.82%. Comparing base (d4e0816) to head (528c497).
⚠️ Report is 3 commits behind head on master.

Files with missing lines	Patch %	Lines
pymilvus/client/entity_helper.py	93.33%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3401      +/-   ##
==========================================
+ Coverage   90.76%   90.82%   +0.05%     
==========================================
  Files          64       64              
  Lines       13887    13837      -50     
==========================================
- Hits        12605    12567      -38     
+ Misses       1282     1270      -12     

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[XuanYang-cn]

Clean refactor — consolidating four copies of the same mapping into one dict is the right call, and replacing the list-comprehension side-effect pattern with for loops is a nice bonus.

A few things worth addressing:

1. Private symbol accessed cross-module
search_result.py references entity_helper._ARRAY_ELEMENT_TYPE_TO_ATTR. Since it's now shared across modules, consider dropping the leading underscore to make it explicitly public.

2. Constant defined below first use
_ARRAY_ELEMENT_TYPE_TO_ATTR is declared around line 1178, after the functions that reference it. It works at runtime, but the convention is to put module-level constants above their first consumer. Easy move.

3. Silent skip for unsupported types in search_result.py
The refactored loop silently produces a shorter list when attr is None and ith_array is not None (the elif just falls through). This was a pre-existing bug, not introduced here, but since we're touching this function anyway it's a good opportunity to add the same raise MilvusException(...) guard that entity_helper.py uses.

4. Docstring
The extract_array_rows docstring restates what the parameter name already communicates. Can be dropped.

None of these are blockers — the core change is correct and a clear improvement.