mcs/tso: add log to show the progress of group cleaning up

[JmPotato]

What problem does this PR solve?

Issue Number: ref #6589.

What is changed and how does it work?

Add log to show the progress of group cleaning up.

Check List

Tests

• Unit test
• Integration test

Release note

None.

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• bufferflies
• lhy1024

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[codecov]

Codecov Report

Merging #6971 (e3817cf) into master (346e771) will decrease coverage by 0.01%.
The diff coverage is 100.00%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #6971      +/-   ##
==========================================
- Coverage   74.36%   74.35%   -0.01%     
==========================================
  Files         427      427              
  Lines       45334    45351      +17     
==========================================
+ Hits        33711    33723      +12     
- Misses       8659     8667       +8     
+ Partials     2964     2961       -3     

Flag	Coverage Δ
unittests	74.35% <100.00%> (-0.01%)	⬇️

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[JmPotato]

/merge

[ti-chi-bot]

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[ti-chi-bot]

This pull request has been accepted and is ready to merge.

Commit hash: e3817cf