fix: [Backport] Mark channel checkpoint dropped prevent cp lag metrics leakage (#32454)

[congqixia]

Cherry-pick from 2.3
pr: #32454
See also #31506 #31508

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[sre-ci-robot]

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[mergify]

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

[congqixia]

/run-cpu-e2e

[codecov]

Codecov Report

Attention: Patch coverage is 84.61538% with 2 lines in your changes are missing coverage. Please review.

Project coverage is 82.19%. Comparing base (c35eaaa) to head (cfe62d9).
Report is 10 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master   #33198      +/-   ##
==========================================
+ Coverage   82.17%   82.19%   +0.02%     
==========================================
  Files        1009     1009              
  Lines      128822   128835      +13     
==========================================
+ Hits       105856   105901      +45     
+ Misses      18961    18935      -26     
+ Partials     4005     3999       -6     

Files	Coverage Δ
internal/datacoord/services.go	85.72% <100.00%> (+0.01%)	⬆️
internal/datacoord/meta.go	93.96% <83.33%> (+1.36%)	⬆️

... and 33 files with indirect coverage changes

[longjiquan]

/lgtm