Implement export_multiline support for Array[String] and Dictionary

For arrays, specifically check if it's a string array and pass the
type on to the editor. For dictionaries, save the hint on the type and
use it later to draw the multiline editor, except for when adding a
string key, because that doesn't make much sense. All string values
however will be drawn as multiline.

editor/editor_properties_array_dict.cpp

@@ -818,6 +818,10 @@ void EditorPropertyDictionary::_change_type_menu(int p_index) {
 	update_property();
 }
 
+void EditorPropertyDictionary::setup(PropertyHint p_hint) {
+	property_hint = p_hint;
+}
+
 void EditorPropertyDictionary::update_property() {
 	Variant updated_val = get_edited_object()->get(get_edited_property());
 
@@ -929,7 +933,13 @@ void EditorPropertyDictionary::update_property() {
 					prop = editor;
 				} break;
 				case Variant::STRING: {
-					prop = memnew(EditorPropertyText);
+					if (i != amount && property_hint == PROPERTY_HINT_MULTILINE_TEXT) {
+						// If this is NOT the new key field and there's a multiline hint,
+						// show the field as multiline
+						prop = memnew(EditorPropertyMultilineText);
+					} else {
+						prop = memnew(EditorPropertyText);
+					}
 
 				} break;