enhance: make estimate json stats size more accurate

[zhagnlu]

#42533

[sre-ci-robot]

[ci-v2-notice]
Notice: We are gradually rolling out the new ci-v2 system.

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[codecov]

Codecov Report

❌ Patch coverage is 37.77778% with 28 lines in your changes missing coverage. Please review.
✅ Project coverage is 75.98%. Comparing base (7d19c40) to head (a9a7bca).
⚠️ Report is 4 commits behind head on master.

Files with missing lines	Patch %	Lines
internal/datanode/index/task_stats.go	0.00%	10 Missing ⚠️
internal/querynodev2/segments/segment_loader.go	50.00%	8 Missing and 1 partial ⚠️
internal/util/indexcgowrapper/index.go	0.00%	9 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           master   #45875       +/-   ##
===========================================
- Coverage   82.72%   75.98%    -6.74%     
===========================================
  Files         524     1888     +1364     
  Lines       82346   294979   +212633     
===========================================
+ Hits        68118   224143   +156025     
- Misses      14228    63405    +49177     
- Partials        0     7431     +7431     

Components	Coverage Δ
Client	78.17% <ø> (∅)
Core	82.72% <ø> (ø)
Go	74.03% <42.85%> (∅)

Files with missing lines	Coverage Δ
pkg/util/paramtable/component_param.go	97.64% <100.00%> (ø)
internal/querynodev2/segments/segment_loader.go	57.97% <50.00%> (ø)
internal/util/indexcgowrapper/index.go	55.90% <0.00%> (ø)
internal/datanode/index/task_stats.go	52.69% <0.00%> (ø)

... and 1360 files with indirect coverage changes

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[mergify]

@zhagnlu cpu-e2e job failed, comment /run-cpu-e2e can trigger the job again.

[zhagnlu]

/run-cpu-e2e

[sparknack]

/lgtm

[sre-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: zhagnlu, zhengbuqian

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