enhance: Skip loading pk index for sorted segment in loader

[congqixia]

Related to #39339
Previous PR #39389 only skips append index into segment

Also related to #39428

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 11 lines in your changes missing coverage. Please review.

Project coverage is 80.98%. Comparing base (cb959cd) to head (67ca4d9).
Report is 5 commits behind head on master.

Files with missing lines	Patch %	Lines
internal/querynodev2/segments/segment.go	0.00%	10 Missing and 1 partial ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##           master   #39437   +/-   ##
=======================================
  Coverage   80.97%   80.98%           
=======================================
  Files        1408     1408           
  Lines      198569   198580   +11     
=======================================
+ Hits       160797   160821   +24     
+ Misses      32100    32087   -13     
  Partials     5672     5672           

Components	Coverage Δ
Client	79.50% <ø> (ø)
Core	69.47% <ø> (ø)
Go	82.92% <0.00%> (+<0.01%)	⬆️

Files with missing lines	Coverage Δ
internal/querynodev2/segments/segment.go	66.95% <0.00%> (-0.72%)	⬇️

... and 29 files with indirect coverage changes

[liliu-z]

/approve
/lgtm

[sre-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: congqixia, liliu-z

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