Convert the feed block into a view

It is possible to do this! #2287073: Allow views contextual filters to expose the context using argument validation plugins → added contextual filters to Views blocks. The only piece that we're missing to make this happen is a ContextProvider for Feed entities. But one was already written for 📌 Add a ContextProvider for Feeds Needs review . I've rerolled that patch and have a context-selected feed block that's provided by Views working on my local test site right now. I'm going to work on getting the ContextProvider ready in the other issue.

Postponing on 📌 Add a ContextProvider for Feeds Needs review .