codec(ticdc): adjust decoder interface to make it reusable

[3AceShowHand]

What problem does this PR solve?

Issue Number: close #8861

What is changed and how it works?

• add a new method AddKeyValue to the decoder interface
• adjust consumer to use the method.

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

`None`

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• CharlesCheung96
• asddongmen

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[CharlesCheung96]

/merge

[ti-chi-bot]

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

Commit hash: 6656e24

[3AceShowHand]

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[3AceShowHand]

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