feat: add collection level balancer switch

[sunby]

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[mergify]

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[codecov]

Codecov Report

Attention: 54 lines in your changes are missing coverage. Please review.

Comparison is base (fb9d64a) 79.83% compared to head (82a6fb6) 79.93%.
Report is 18 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master   #30411      +/-   ##
==========================================
+ Coverage   79.83%   79.93%   +0.10%     
==========================================
  Files         954      954              
  Lines      134860   134914      +54     
==========================================
+ Hits       107660   107839     +179     
+ Misses      23538    23416     -122     
+ Partials     3662     3659       -3     

Files	Coverage Δ
internal/querycoordv2/checkers/balance_checker.go	92.47% <100.00%> (+0.08%)	⬆️
internal/querycoordv2/checkers/channel_checker.go	79.62% <100.00%> (+0.12%)	⬆️
internal/querycoordv2/checkers/leader_checker.go	86.36% <100.00%> (+0.10%)	⬆️
internal/querycoordv2/checkers/segment_checker.go	86.11% <100.00%> (+0.04%)	⬆️
internal/querycoordv2/checkers/checker.go	90.00% <81.81%> (-10.00%)	⬇️
internal/querycoordv2/checkers/index_checker.go	79.24% <0.00%> (-1.53%)	⬇️
internal/querycoordv2/checkers/controller.go	78.90% <26.66%> (-16.51%)	⬇️
internal/querycoordv2/ops_services.go	0.00% <0.00%> (ø)

... and 22 files with indirect coverage changes

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