feat: add support for useragent Fluent filter

[csabatuz-chess]

This PR adds support for using the https://github.com/bungoume/fluent-plugin-ua-parser Fluent plugin where Fluent plugins are applicable.

Depends on: kube-logging/fluentd-images#88

[csabatuz-chess]

I'm stuck a bit, can't really interpret the failing E2E test, or connect it to my changeset.

[OverOrion]

I'm stuck a bit, can't really interpret the failing E2E test, or connect it to my changeset.

I reran the CI and it passed, seems like the TestVolumeDrain_Downscale might be flaky, sorry about that!

[csabatuz-chess]

The directives don't seem to render right in Markdown, that's why I left with ```yaml.

Not sure what's downstream, if this'll be straightened out in the docs, just checking in if this was intended.

[OverOrion]

The directives don't seem to render right in Markdown, that's why I left with ```yaml.
Not sure what's downstream, if this'll be straightened out in the docs, just checking in if this was intended.

Yeah, that is alright, it is deliberate. The generated *.md files will be consumed by Hugo and it will render it properly (indentation and highlighting wise as well).