improvement: move index-related code into standalone bundle

[passioneight]

Undoubtedly, using an index has many benefits. But just because an index is needed, it doesn't mean the entire ecommerce framework is needed.

It would be great if the index-related code was separated into a standalone bundle (maybe even as part of the core?). This also implies getting rid of the "product" context. That is, instead of having a "product index" we'll just have an "index". Obviously, removing the context is just for semantic reasons.

Wdyt?

[github-actions]

Thanks a lot for reporting the issue. We did not consider the issue as "Pimcore:Priority", "Pimcore:ToDo" or "Pimcore:Backlog", so we're not going to work on that anytime soon. Please create a pull request to fix the issue if this is a bug report. We'll then review it as quickly as possible. If you're interested in contributing a feature, please contact us first here before creating a pull request. We'll then decide whether we'd accept it or not. Thanks for your understanding.