TUI rewrite

[dfordivam]

• Removes use of existentials. fixes Remove existential types in TUI #1217

• Makes use of GHC.Generics to take care of the Menu boilerplate

• Improves the structure of code as each widget now need to implement the instance of BaseWidget, which captures the two essential parts, rendering and event handling.

• The structure of the widget state matches directly to the "tree" structure of widgets. And the use of enums, like Mode, have been removed.

• The input fields are more generic and we can nest them, like EditInput is being used inside SelectInput

• The value of input fields can be modified like this

  compileGHCMenu % innerWidget % GenericMenu.fields % CompileGHCMenu.installTargetsF % EditInput.editInputOverlay % innerWidget % EditInput.editor %~ Edit.applyEdit (const (textZipper ["new-value"] Nothing))

• The child widget does not modify the state of parent (as it was earlier being done via lens)

• The 'quit' key handling logic is now mostly part of the BasicOverlay abstraction, and has been removed from the event handlers of individual widgets.

• We can even do nesting of GenericMenu, in case we want to make fancy sub-menus

[lsmor]

I am not able to fully review this as the code is way more complex than my knowledge 😅 . My understading is:

• Menus are defined by two parallel datatypes The "Fields" + "Options", and then this GenericMenu thing which I barely understand... Instead of Having "Options" + list of fields as before.
• Existentials are hidden behind TypeClasses + Data.Some if I understand correctly.
• I don't get the Overlays part. AFAIU, brick dispatches events to the frontward layers, so there is no need to pass events to the "child"/overlayed widget... but maybe I got this wrong