Remove deprecation warnings & Clean up api.

Author: SaadArdati

lib/src/transformers/node_transformers/passive_row_column_transformer.dart

@@ -314,7 +314,7 @@ class PassiveRowColumnWidget extends StatelessWidget {
             withScroll: true,
           );
 
-    if (isTestLayout) {
+    if (kIsTestLayout) {
       return DecoratedBox(
         decoration: BoxDecoration(
           border: Border.all(color: Colors.green, width: 1),

lib/src/transformers/node_transformers/passive_stack_transformer.dart

@@ -202,7 +202,7 @@ class PassiveStackTransformer extends NodeWidgetTransformer<BaseNode> {
     //   );
     // }
 
-    if (isTestLayout) {
+    if (kIsTestLayout) {
       return DecoratedBox(
         decoration: BoxDecoration(
           border: Border.all(color: Colors.yellow, width: 2),

lib/src/transformers/node_transformers/passive_text_transformer.dart

@@ -17,7 +17,7 @@ class PassiveTextTransformer extends NodeWidgetTransformer<TextNode> {
     WidgetBuildSettings settings = const WidgetBuildSettings(),
   ]) {
     final Widget child = PassiveTextWidget(node: node, settings: settings);
-    if (isTestLayout) {
+    if (kIsTestLayout) {
       return DecoratedBox(
         decoration: BoxDecoration(
           border: Border.all(color: Colors.red, width: 2),