fix: Use channel cp as the dml&start position for import segments (#30107)

[bigsheeper]

This PR discontinuing the subscription to the mq and, instead, employing the channel checkpoint as the DML and starting position for the import segments.

issue: #30106

pr: #30107

[mergify]

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

[codecov]

Codecov Report

Attention: 5 lines in your changes are missing coverage. Please review.

Comparison is base (079ddbf) 82.22% compared to head (fdfa873) 82.23%.
Report is 5 commits behind head on 2.3.

Additional details and impacted files

@@           Coverage Diff           @@
##              2.3   #30133   +/-   ##
=======================================
  Coverage   82.22%   82.23%           
=======================================
  Files         836      836           
  Lines      120655   120634   -21     
=======================================
- Hits        99213    99201   -12     
+ Misses      18201    18198    -3     
+ Partials     3241     3235    -6     

Files	Coverage Δ
internal/datanode/services.go	82.85% <100.00%> (+1.40%)	⬆️
internal/datacoord/services.go	85.73% <58.33%> (-0.31%)	⬇️

... and 10 files with indirect coverage changes

[bigsheeper]

/run-cpu-e2e

[czs007]

/approve

[sre-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: bigsheeper, czs007

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• internal/datacoord/OWNERS [czs007]
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[czs007]

/lgtm