enhance: reduce stats task cost by skipping ser/de

[tedxu]

See #37234

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Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 69.40%. Comparing base (5fb597b) to head (be8cc56).
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Additional details and impacted files

@@             Coverage Diff             @@
##           master   #39568       +/-   ##
===========================================
- Coverage   80.97%   69.40%   -11.57%     
===========================================
  Files        1408      302     -1106     
  Lines      198881    27065   -171816     
===========================================
- Hits       161041    18785   -142256     
+ Misses      32151     8280    -23871     
+ Partials     5689        0     -5689     

Components	Coverage Δ
Client	∅ <ø> (∅)
Core	69.40% <ø> (-0.16%)	⬇️
Go	∅ <ø> (∅)

see 1113 files with indirect coverage changes

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[tedxu]

In this PR the sort cost fairly depends on the partial order of the original dataset. If the original dataset is ordered, the CPU and memory cost can be negligible. I've also tested the worst case, for 1M rows the cost is as follows (2seconds & 4.5GB):

BenchmarkSort/sort-8         	       1	2409850417 ns/op	4545456624 B/op	42113988 allocs/op

The worst cost is still an improvement compares to current implementation. The primary cost comes from the Slice operation in arrow, which is not easy to optimize in Milvus's current structure.

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