Configure pat-modal and pat-inject for formaction

[cillianderoiste]

Currently buttons with a formaction attribute use the configuration of the containing form element (IIUC) and can't be configured individually. This makes it tricky to use a modal for some buttons and an injection (e.g. notification) for others.

One workaround for this is to use pat-inject also for modals, and include the container html for modals in the response: https://github.com/quaive/ploneintranet/pull/436

[pilz]

@cillianderoiste do we still need this?