fix: [2.5] Fix slow dist handle and slow observe

[bigsheeper]

1. Provide partition&channel level indexing in the collection target.
2. Make SegmentAction not wait for distribution.
3. Remove scheduler and target manager mutex
4. Optimize logging to reduce CPU overhead.

issue: #37630

pr: #38566

[codecov]

Codecov Report

Attention: Patch coverage is 89.49580% with 25 lines in your changes missing coverage. Please review.

Project coverage is 82.86%. Comparing base (055cbe1) to head (142ac44).

Files with missing lines	Patch %	Lines
internal/querycoordv2/task/scheduler.go	84.96%	18 Missing and 2 partials ⚠️
...rnal/querycoordv2/observers/collection_observer.go	83.33%	4 Missing ⚠️
internal/querycoordv2/meta/target.go	98.24%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##              2.5   #38905       +/-   ##
===========================================
+ Coverage   69.45%   82.86%   +13.40%     
===========================================
  Files         294     1089      +795     
  Lines       26419   169066   +142647     
===========================================
+ Hits        18349   140091   +121742     
- Misses       8070    23403    +15333     
- Partials        0     5572     +5572     

Components	Coverage Δ
Client	78.26% <ø> (∅)
Core	∅ <ø> (∅)
Go	83.03% <89.49%> (∅)

Files with missing lines	Coverage Δ
internal/querycoordv2/dist/dist_handler.go	96.13% <100.00%> (ø)
internal/querycoordv2/meta/target_manager.go	86.93% <100.00%> (ø)
internal/querycoordv2/task/action.go	96.66% <100.00%> (ø)
internal/querycoordv2/utils/util.go	85.54% <100.00%> (ø)
internal/querynodev2/services.go	86.38% <100.00%> (ø)
pkg/metrics/querycoord_metrics.go	100.00% <ø> (ø)
internal/querycoordv2/meta/target.go	92.94% <98.24%> (ø)
...rnal/querycoordv2/observers/collection_observer.go	86.52% <83.33%> (ø)
internal/querycoordv2/task/scheduler.go	87.01% <84.96%> (ø)

... and 1374 files with indirect coverage changes

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