Refactor: add a separate Prompt view

So far, confirmations and prompts were handled by the same view, context, and
controller, with a bunch of conditional code based on whether the view is
editable. This was more or less ok so far, since it does save a little bit of
code duplication; however, now we need separate views, because we don't have
dynamic keybindings, but we want to map "confirm" to different keys in
confirmations (the "universal.confirm" user config) and prompts (hard-coded to
enter, because it doesn't make sense to customize it there).

It also allows us to get rid of the conditional code, which is a nice benefit;
and the code duplication is actually not *that* bad.

pkg/integration/components/views.go

@@ -128,6 +128,10 @@ func (self *Views) Confirmation() *ViewDriver {
 	return self.regularView("confirmation")
 }
 
+func (self *Views) Prompt() *ViewDriver {
+	return self.regularView("prompt")
+}
+
 func (self *Views) CommitMessage() *ViewDriver {
 	return self.regularView("commitMessage")
 }