[ui] GraphEditor: Move ChoiceParam control to its own file

Start modularization of attribute controls for better readability
and maintenance.
Make Choice control independent from the MeshroomUI API.

meshroom/ui/qml/GraphEditor/AttributeControls/Choice.qml

@@ -0,0 +1,34 @@
+import QtQuick
+import QtQuick.Controls
+import QtQuick.Layouts
+
+import MaterialIcons
+import Controls
+
+/**
+ * A combobox-type control with a single current `value` and a list of possible `values`.
+ * Provides filtering capabilities and support for custom values (i.e: `value` not in `values`).
+ */
+RowLayout {
+    id: root
+
+    required property var value
+    required property var values
+
+    signal editingFinished(var value)
+
+    FilterComboBox {
+        id: comboBox
+
+        Layout.fillWidth: true
+        sourceModel: root.values
+        inputValue: root.value
+        onEditingFinished: value => root.editingFinished(value)
+    }
+
+    MaterialLabel {
+        visible: !comboBox.validValue
+        text: MaterialIcons.warning
+        ToolTip.text: "Custom value detected"
+    }
+}