fix: add GetSegments optimization to avoid meta mutex competition

[zhagnlu]

pr: #31025

[mergify]

@zhagnlu Please associate the related pr of master to the body of your Pull Request. (eg. “pr: #”)

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 82.22%. Comparing base (a5350f6) to head (4de0535).
Report is 2 commits behind head on 2.3.

Additional details and impacted files

@@            Coverage Diff             @@
##              2.3   #31026      +/-   ##
==========================================
+ Coverage   82.20%   82.22%   +0.02%     
==========================================
  Files         843      843              
  Lines      121908   121915       +7     
==========================================
+ Hits       100214   100247      +33     
+ Misses      18461    18448      -13     
+ Partials     3233     3220      -13     

Files	Coverage Δ
internal/datacoord/meta.go	88.75% <100.00%> (+0.11%)	⬆️
internal/datacoord/segment_manager.go	92.21% <100.00%> (+1.87%)	⬆️

... and 13 files with indirect coverage changes

[czs007]

/approve
/lgtm

[sre-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: czs007, zhagnlu

The full list of commands accepted by this bot can be found here.

The pull request process is described here

Needs approval from an approver in each of these files:

• internal/datacoord/OWNERS [czs007]

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment