Flush interval per output or per output

Would it be possible to support `Flush` as a per input or per output setting?

The reason for this request is that different inputs may be accepting logs at different rates, and different output APIs might have different batching requirements, so to efficiently batch data, a different flush interval per input could be best in some cases. Consider may be one input is uptaking data very slowly, and another is getting data very fast.

The issue names no files, tests, or entry points. Start by locating the existing global Flush setting and the input and output configuration paths. Done means flush intervals can be configured independently for inputs or outputs while preserving existing behavior when no per-component setting is provided.

Written by the indexing model from the issue text.