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/gui/controllers.go

@@ -193,6 +193,7 @@ func (gui *Gui) resetHelpersAndControllers() {
 	statusController := controllers.NewStatusController(common)
 	commandLogController := controllers.NewCommandLogController(common)
 	confirmationController := controllers.NewConfirmationController(common)
+	promptController := controllers.NewPromptController(common)
 	suggestionsController := controllers.NewSuggestionsController(common)
 	jumpToSideWindowController := controllers.NewJumpToSideWindowController(common, gui.handleNextTab)
 
@@ -399,6 +400,10 @@ func (gui *Gui) resetHelpersAndControllers() {
 		confirmationController,
 	)
 
+	controllers.AttachControllers(gui.State.Contexts.Prompt,
+		promptController,
+	)
+
 	controllers.AttachControllers(gui.State.Contexts.Suggestions,
 		suggestionsController,
 	)