feat: allow pass-by source enumerator check

[tabVersion]

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What's changed and what's your intention?

introduce a debug-mode-only attr debug_splits, it will return the given splits instead of requesting the broker. \

an example here

# producing 101 messages to the topic
for i in {0..100}; do echo "{\"a\": $i}^{\"a\": $i, \"b\": \"$i\"}" | kcat -P -b 127.0.0.1:9092 -t test_1 -K ^ -H "header1=v1" -H "header2=v2"; done

--- psql ---

create table t2 ( a int, b varchar ) with ( connector = 'kafka', properties.bootstrap.server = '127.0.0.1:9092', topic = 'test_1' , debug_splits = '[{"split_info": {"partition": 0, "start_offset": -1, "stop_offset": null, "topic": "test_1"}, "split_type": "kafka"}]') format plain encode json ;

dev=> select count(*) from t2 ;
 count
-------
    50
(1 row)

Checklist

• I have written necessary rustdoc comments.
• I have added necessary unit tests and integration tests.
• I have added test labels as necessary.
• I have added fuzzing tests or opened an issue to track them.
• My PR contains breaking changes.
• My PR changes performance-critical code, so I will run (micro) benchmarks and present the results.
• My PR contains critical fixes that are necessary to be merged into the latest release.

Documentation

it is for dev use only, no need for doc change

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Release note