refactor(source): respect max chunk size in source connector parser

[stdrc]

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What's changed and what's your intention?

In SourceStreamChunkBuilder, with the information of SourceCtrlOps, we can actually restrict the chunk size early during chunk building, instead emitting large chunks first and cutting them into small ones later in apply_rate_limit. This has two benefits:

1. Reduce the chunk splitting cost in apply_rate_limit used by FetchExecutor, FsSourceExecutor, SourceBackfillExecutor and SourceExecutor.
2. Source connectors and parsers can utilize their better understanding of the payload (e.g. transaction information), to avoid blindly cutting chunks at random positions.

Main changes happened in this PR:

1. Change SourceCtrlOpts::rate_limit: Option<u32> to split_txn: bool.

   This is because we already pass in a limited chunk size (basically min(stream_chunk_size, rate_limit_burst)) via SourceCtrlOpts::chunk_size. We still need split_txn to control whether we need to cut chunks during (CDC) transactions, as concluded here.

2. Simplify SourceStreamChunkRowWriter, by directly store a reference to SourceStreamChunkBuilder inside it.

3. Rewrite SourceStreamChunkBuilder to allow creating chunk during writing to SourceStreamChunkRowWriter. The trick is to add a ready_chunks field.

   This is because that it's possible to parse multiple rows from one SourceMessage, while the parser API doesn't use async stream to yield rows, instead, it directly write to SourceStreamChunkRowWriter.

Checklist

• I have written necessary rustdoc comments
• I have added necessary unit tests and integration tests
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• My PR contains breaking changes. (If it deprecates some features, please create a tracking issue to remove them in the future).
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Documentation

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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): remove chunk splitting logic in apply_rate_limit #19826
• refactor(source): respect max chunk size in source connector parser #19698 👈 (View in Graphite)
• refactor(cdc source): merge cdc heartbeat chunk builder & data chunk builder #19671
• refactor(connector): re-arrange the connector::parser module for better readibility #19697
• main

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[tabVersion]

any context about the refactor?

[stdrc]

any context about the refactor?

still WIP, will add description when it's ready