Add a Netflow/IPFIX input plugin to Fluent-Bit, please

**Is your feature request related to a problem? Please describe.**
I want to process Netflow/IPFIX data. FileBeat and LogStash, for instance, have an input plugin to do so. FluentD too.

**Describe the solution you'd like**
I'd like Fluent-Bit has a Netflow/IPFIX input plugin to act as a Netflow/IPFIX collector.

**Describe alternatives you've considered**
Use anothe log collector/forwarder.

Thanks!

The issue names no files, tests, or entry points. Start by studying Fluent Bit's existing input plugins and how they collect and parse network data, then define the NetFlow/IPFIX protocol scope, configuration, and test coverage; done means Fluent Bit can collect and process the requested data as a supported input.

Written by the indexing model from the issue text.