fix(#3634055): refuse a paragraph save that changes a published page in publish-only mode

In publish-only mode, a paragraph saved by itself, such as over JSON:API, could put an error on a published page, because Paragraphs doesn't make a new revision for that save. Vale now treats such a save as a publishing save when a published host shows the revision being changed. A form that validates the paragraph for its host still lets a draft of that host save with its errors. Kernel and functional tests cover a published host, a draft host, a new revision, nested paragraphs and the JSON:API PATCH