refactor(connector): re-arrange the connector::parser module for better readibility

[stdrc]

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What's changed and what's your intention?

There were too many unrelated things inside connector/src/parser/mod.rs, this PR moves some relatively independent units into separate submodules.

Only moves code, no other changes.

Checklist

• I have written necessary rustdoc comments
• I have added necessary unit tests and integration tests
• I have added test labels as necessary. See details.
• I have added fuzzing tests or opened an issue to track them. (Optional, recommended for new SQL features Sqlsmith: Sql feature generation #7934).
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Release note

If this PR includes changes that directly affect users or other significant modifications relevant to the community, kindly draft a release note to provide a concise summary of these changes. Please prioritize highlighting the impact these changes will have on users.

[stdrc]

• refactor(source): respect max chunk size in source connector parser #19698 : 2 dependent PRs (#19826 , #19863 )
• refactor(cdc source): merge cdc heartbeat chunk builder & data chunk builder #19671
• refactor(connector): re-arrange the connector::parser module for better readibility #19697 👈 (View in Graphite)
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[xiangjinwu]

Thanks!

[tabVersion]

thanks