Add component-factory type to Slint language

Add a type "component-factory" to the Slint language.

internal/compiler/expression_tree.rs

@@ -1224,6 +1224,7 @@ impl Expression {
         match ty {
             Type::Invalid
             | Type::Callback { .. }
+            | Type::ComponentFactory
             | Type::Function { .. }
             | Type::Void
             | Type::InferredProperty