fix: reduce didn't handle offset without limit and reduceStopForBest correctly

[xiaofan-luan]

fix #32059

this pr fix two issues:

offset is not handled correctly without specify a limit
reduceStopForBest doesn't guarantee to return limit result even if there are more result when there is small segment

[sre-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: xiaofan-luan

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Needs approval from an approver in each of these files:

• internal/proxy/OWNERS [xiaofan-luan]
• internal/querynodev2/segments/OWNERS [xiaofan-luan]
• pkg/util/OWNERS [xiaofan-luan]

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[mergify]

@xiaofan-luan E2e jenkins job failed, comment /run-cpu-e2e can trigger the job again.

[MrPresent-Han]

/lgtm

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 81.63%. Comparing base (1b76766) to head (304f3c7).
Report is 17 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master   #32089      +/-   ##
==========================================
- Coverage   81.63%   81.63%   -0.01%     
==========================================
  Files         978      989      +11     
  Lines      121665   121584      -81     
==========================================
- Hits        99326    99256      -70     
+ Misses      18525    18520       -5     
+ Partials     3814     3808       -6     

Files	Coverage Δ
internal/proxy/task_query.go	80.90% <100.00%> (+0.81%)	⬆️
internal/querynodev2/segments/result.go	80.12% <100.00%> (-4.64%)	⬇️
pkg/util/typeutil/schema.go	85.00% <100.00%> (+0.19%)	⬆️

... and 246 files with indirect coverage changes