Lowering log level of "chunk bytes limit exceeds for an emitted event stream" logs to trace

### Is your feature request related to a problem? Please describe.

Hey team 👋

From what I have gathered, fluentd did not split chunks if the event stream exceeds the chunk bytes limit, but this was changed in https://github.com/fluent/fluentd/commit/b5f2e9fe4b2376ce0624cc756598e90bb64970d5.
Since we are now splitting chunks and retrying the chunks, I think this log (`chunk bytes limit exceeds for an emitted event stream`) is now more informational (and for debugging really) more than indicative of a potential issue.

### Describe the solution you'd like

What are your thoughts on lowering this log line from `warn` to something like `trace`?

### Describe alternatives you've considered

Leaving it - but it does generate a lot of logs

### Additional context

_No response_

Search the repository for the exact log message "chunk bytes limit exceeds for an emitted event stream" and inspect the surrounding logging code. Check nearby tests if present; done means the message is emitted at trace rather than warn without changing the chunk-splitting or retry behavior.

Written by the indexing model from the issue text.