fix: [2.4] rbac custom group privilege level check

[shaoting-huang]

cherry-pick from master: #39164
related: related: #39086

[xiaofan-luan]

/lgtm
/approve

[sre-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: shaoting-huang, xiaofan-luan

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• internal/proxy/OWNERS [xiaofan-luan]
• internal/rootcoord/OWNERS [xiaofan-luan]
• pkg/util/OWNERS [xiaofan-luan]
• tests/integration/OWNERS [xiaofan-luan]

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[codecov]

Codecov Report

Attention: Patch coverage is 89.36170% with 10 lines in your changes missing coverage. Please review.

Project coverage is 79.50%. Comparing base (af22644) to head (c330f36).
Report is 1 commits behind head on 2.4.

Files with missing lines	Patch %	Lines
internal/rootcoord/root_coord.go	88.37%	4 Missing and 1 partial ⚠️
pkg/util/paramtable/rbac_param.go	91.42%	2 Missing and 1 partial ⚠️
internal/rootcoord/meta_table.go	0.00%	1 Missing ⚠️
pkg/util/constant.go	93.33%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##              2.4   #39194      +/-   ##
==========================================
- Coverage   80.44%   79.50%   -0.94%     
==========================================
  Files        1077     1077              
  Lines      169731   169767      +36     
==========================================
- Hits       136534   134979    -1555     
- Misses      28713    30287    +1574     
- Partials     4484     4501      +17     

Files with missing lines	Coverage Δ
internal/proxy/impl.go	83.86% <ø> (-0.01%)	⬇️
internal/proxy/util.go	90.47% <ø> (-0.21%)	⬇️
internal/rootcoord/meta_table.go	83.97% <0.00%> (ø)
pkg/util/constant.go	96.15% <93.33%> (-0.68%)	⬇️
pkg/util/paramtable/rbac_param.go	97.14% <91.42%> (-2.09%)	⬇️
internal/rootcoord/root_coord.go	87.90% <88.37%> (-0.03%)	⬇️

... and 95 files with indirect coverage changes