Track stabilization of --experimental-bootstrap-defrag-threshold-megabytes flag

[serathius]

This is tracking issue that tracks graduation of this feature. Let's work towards stabilization of the feature by discussing what steps should be taken for graduation.
Context #13775

[lavacat]

This flag was introduced here #12941

[lavacat]

@serathius I think we should make this flag optional (remove experimental)
As a feature it looks safe to me.

The only concern is if people actually use this. I've tried searching kube docs and it's not mentioned. Also, no interesting results in GitHub search

Do you have an opinion about this flag?

[serathius]

I think the feature is simple enough that we could consider it for graduation, but I think we should double check if non-functional requirements for graduation has been met (has e2e tests). Maintainers just started work on formalizing feature stages and their requirements. Please take a look #14428

After we have formalized requirements for feature I will update all the feature graduation issues like this one and add a checklist to them.