[Metricbeat] Remove EventFetcher and EventsFetcher interface

[ruflin]

After migrating all metricsets (#10774) to the Reporter interfaces, the EventFetcher and EventsFetcher interface can be removed.

[exekias]

what would happen to existing community beats that upgrade libbeat? Not sure how frequently that happens

[ruflin]

@exekias They will break and have to migrate to the new reporter. But in most cases this should be pretty straight forward and I don't think we should wait until 8 to remove this.

[ruflin]

@exekias Assigning this to you for now, hope that is ok.

[mergify]

This pull request is now in conflicts. Could you fix it? 🙏
To fixup this pull request, you can check out it locally. See documentation: https://help.github.com/articles/checking-out-pull-requests-locally/

git fetch upstream
git checkout -b remove-event-fetcher upstream/remove-event-fetcher
git merge upstream/master
git push upstream remove-event-fetcher

[urso]

@ruflin @exekias Have these interfaces already been removed, or shall we resurrect the PR?

[exekias]

I don't think this happened in the end, IIRC there were a few bits still pending in the PR

[ruflin]

Should I best close this PR so someone can follow up with this?

[urso]

I'd love to remove that much code (when working on collector POC these interfaces did contribute to most complexity/code...). If there is something pending lets close and create an issue, otherwise get rid of it now.

[ruflin]

@urso ++. Can someone from the team take this over?

[urso]

Not sure what is missing + I would like someone who is familiar with metricset implementation to change these kind of internals. @jsoriano Can you have a look?

[jsoriano]

Hi, yes, I will take a look 👍

[jsoriano]

Continuing with this in #25093.