Trim21

fix: dumper should write output to DumpName

1

## Summary by CodeRabbit * **New Features** * Database dumps for MySQL and PostgreSQL are now saved directly as compressed files, avoiding stdout. This simplifies export workflows and ensures outputs...

avoid write dump result to stdout

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I'm tring to dump mysql to s3 and I find it write entire content of sql (output of mysqldump) to stdout, make it hard to find out what's happening

Change event_source type from Generator to Iterator

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improve typing, the event_source doesn't need to be a generator. and a generator is a iterator. with the new typing, this would be valid in type checker: ``` import httpx...