UID refactor 4/ Expose readonly UIState

Summary:
Currently state writes can either go through a named handler that is easy to find and debug or they can directly modify the state.

By exposing readonly atoms only we ensure that all state writes go through a UIACtions. This adds consistency and ease of future debugging.

E.g We could add a utility to wrap all ui actions with logging statements

Reviewed By: antonk52

Differential Revision: D47547531

fbshipit-source-id: f88651169d8e7c5f7e31068d64f9aa5b6b573647

desktop/plugins/public/ui-debugger/components/util/UIDebuggerMenuItem.tsx

@@ -39,7 +39,7 @@ export const UIDebuggerMenuItem: React.FC<{
       disabled={onClick == null}
       onClick={() => {
         onClick?.();
-        instance.uiState.isContextMenuOpen.set(false);
+        instance.uiActions.onContextMenuOpen(false);
       }}>
       <Layout.Horizontal center gap="small">
         {icon}