enhance: Add management api to check querycoord balance status

[weiliu1031]

issue: #37783

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[mergify]

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[codecov]

Codecov Report

Attention: Patch coverage is 79.66102% with 12 lines in your changes missing coverage. Please review.

Project coverage is 80.66%. Comparing base (00edec2) to head (7f1cf7a).
Report is 25 commits behind head on master.

Files with missing lines	Patch %	Lines
internal/querycoordv2/ops_services.go	45.45%	10 Missing and 2 partials ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           master   #37784       +/-   ##
===========================================
+ Coverage   68.91%   80.66%   +11.75%     
===========================================
  Files         290     1357     +1067     
  Lines       25471   190977   +165506     
===========================================
+ Hits        17553   154051   +136498     
- Misses       7918    31487    +23569     
- Partials        0     5439     +5439     

Components	Coverage Δ
Client	61.25% <ø> (∅)
Core	68.85% <ø> (-0.07%)	⬇️
Go	83.18% <79.66%> (∅)

Files with missing lines	Coverage Δ
internal/distributed/querycoord/client/client.go	96.85% <100.00%> (ø)
internal/distributed/querycoord/service.go	77.20% <100.00%> (ø)
internal/proxy/management.go	87.44% <100.00%> (ø)
internal/util/mock/grpc_querycoord_client.go	94.87% <100.00%> (ø)
internal/querycoordv2/ops_services.go	85.75% <45.45%> (ø)

... and 1070 files with indirect coverage changes

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[weiliu1031]

/run-cpu-e2e