feat(cdc): rate limit for cdc backfill

[StrikeW]

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What's changed and what's your intention?

Support alter table t1 set backfill_rate_limit = xx for cdc table.

• Extend update_mv_rate_limit_by_table_id to modify the rate_limit of StreamCdcScan node

Tested locally.

#17913

Checklist

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Release note

Support altering backfill_rate_limit of cdc table.

[kwannoel]

Thanks for your work! Could you add e2e_source_test for cdc backfill?

You can reuse the test logic under https://github.com/risingwavelabs/risingwave/blob/main/e2e_test/source/basic/alter/rate_limit_table_kafka.slt.

See that we can set cdc_backfill to 0 initially, and alter it to resume.

[kwannoel]

Rest LGTM

[chenzl25]

LGTM

[kwannoel]

LGTM, thanks!