sinkv2(ticdc): observe row size in MQ sink (#8287)

[ti-chi-bot]

This is an automated cherry-pick of #8287

What problem does this PR solve?

Issue Number: close #8286

What is changed and how it works?

observe row size in MQ sink.

Check List

Tests

• Manual test

Questions

Will it cause performance regression or break compatibility?

No

Do you need to update user documentation, design documentation or monitoring documentation?

No

Release note

Add missing big row metric in MQ sink

[ti-chi-bot]

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[Rustin170506]

/merge

[ti-chi-bot]

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

Commit hash: 20e42e2

[Rustin170506]

/run-verify

[codecov-commenter]

Codecov Report

❗ No coverage uploaded for pull request base (release-6.5@86004ca). Click here to learn what that means.
The diff coverage is n/a.

❗ Current head 7674060 differs from pull request most recent head 20e42e2. Consider uploading reports for the commit 20e42e2 to get more accurate results

Additional details and impacted files

Flag	Coverage Δ
cdc	65.6020% <0.0000%> (?)
dm	55.0307% <0.0000%> (?)
engine	66.5909% <0.0000%> (?)

Flags with carried forward coverage won't be shown. Click here to find out more.

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