fix: [2.4] expand privilege group when list policy in rootcoord

[shaoting-huang]

cherry-pick from: #38758
related: #38757

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 83.37%. Comparing base (b9eb396) to head (b81b248).
Report is 4 commits behind head on 2.4.

Additional details and impacted files

@@            Coverage Diff             @@
##              2.4   #38759      +/-   ##
==========================================
+ Coverage   80.40%   83.37%   +2.97%     
==========================================
  Files        1077      809     -268     
  Lines      169610   143069   -26541     
==========================================
- Hits       136369   119283   -17086     
+ Misses      28744    19302    -9442     
+ Partials     4497     4484      -13     

Files with missing lines	Coverage Δ
internal/metastore/catalog.go	100.00% <ø> (ø)
internal/metastore/kv/rootcoord/kv_catalog.go	82.20% <100.00%> (+0.10%)	⬆️
internal/rootcoord/meta_table.go	83.97% <100.00%> (ø)
internal/rootcoord/root_coord.go	87.93% <100.00%> (+0.34%)	⬆️

... and 307 files with indirect coverage changes

[tedxu]

/lgtm
/approve

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