mounter(ticdc): default value convert to the correct data type (#10804)

[ti-chi-bot]

This is an automated cherry-pick of #10804

What problem does this PR solve?

Issue Number: close #10803

What is changed and how it works?

• convert the datum to the specific column type

Check List

Tests

• Unit test
• Integration test

Questions

Will it cause performance regression or break compatibility?

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

Release note

fix the default value is always string type since not considering data type causes the open-protocol output incorrect type value

[3AceShowHand]

this PR is cherry-pick by #108989, this one can be closed.

[ti-chi-bot]

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