enhance: Remove QueryCoord's scheduling of L0 segments

[weiliu1031]

issue: #39551
This PR remove querycoord's scheduling of l0 segments:

• only load l0 segment when watch channel
• only release l0 segment when release channel or sync data distribution

[sre-ci-robot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

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Needs approval from an approver in each of these files:

• internal/querycoordv2/checkers/OWNERS
• internal/querycoordv2/dist/OWNERS
• internal/querycoordv2/meta/OWNERS
• internal/querycoordv2/observers/OWNERS
• internal/querycoordv2/task/OWNERS
• internal/querycoordv2/utils/OWNERS
• internal/querynodev2/OWNERS
• pkg/proto/OWNERS

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[mergify]

@weiliu1031 E2e jenkins job failed, comment /run-cpu-e2e can trigger the job again.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 69.56%. Comparing base (844df76) to head (17f2571).
Report is 1 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master   #39552   +/-   ##
=======================================
  Coverage   69.56%   69.56%           
=======================================
  Files         300      300           
  Lines       26985    26985           
=======================================
  Hits        18772    18772           
  Misses       8213     8213           

Components	Coverage Δ
Client	∅ <ø> (∅)
Core	69.56% <ø> (ø)
Go	∅ <ø> (∅)

[weiliu1031]

rerun ut