refactor(ui): One QML file per screen; the HDMI boost's setup screens and backend commands removed

ui/qml/Input.qml

@@ -0,0 +1,14 @@
+// The input in use (controller, keyboard or remote) and the button names
+// shown for it.
+pragma Singleton
+import QtQuick
+
+QtObject {
+    property string type: "keyboard"
+    readonly property var glyphs: ({
+        controller: { toggle: "A", choose: "◀ ▶", reapply: "Y", quit: "B", apply: "X", ok: "A", back: "B" },
+        keyboard: { toggle: "Space", choose: "← →", reapply: "R", quit: "Esc", apply: "Enter", ok: "Enter", back: "Esc" },
+        remote: { toggle: "OK", choose: "◀ ▶", reapply: "Red", quit: "Back", apply: "↓ Apply", ok: "OK", back: "Back" }
+    })
+    readonly property var g: glyphs[type]
+}