refine the default values for segcore threadpool size

[MrPresent-Han]

/kind improvement
related: #26028

[codecov]

Codecov Report

Merging #27406 (2df8b1d) into master (a8ce1b6) will decrease coverage by 0.01%.
Report is 1 commits behind head on master.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master   #27406      +/-   ##
==========================================
- Coverage   81.45%   81.44%   -0.01%     
==========================================
  Files         803      803              
  Lines      114586   114586              
==========================================
- Hits        93335    93326       -9     
- Misses      18069    18075       +6     
- Partials     3182     3185       +3     

Files	Coverage Δ
pkg/util/paramtable/component_param.go	98.08% <ø> (ø)

... and 10 files with indirect coverage changes

[congqixia]

/lgtm

[congqixia]

please link to previous component param pr

[xiaofan-luan]

/lgtm
/approve

[sre-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: congqixia, MrPresent-Han, xiaofan-luan

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