gzip compressor: stop unnecessary re-compression when the chunk is already compressed

[daipom]

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

It appears the gzip compressor of out_s3 does unnecessary re-compression when the chunk is already compressed.

https://github.com/fluent/fluent-plugin-s3/blob/803cac2094885d5db5d902ab104a883008eda8ec/lib/fluent/plugin/out_s3.rb#L615-L631

Describe the solution you'd like

The logic should be linked to Buffer settings, like out_file.

Describe alternatives you've considered

None.

Additional context

No response