Tabs animation and selected index fixes (#8377)

* fix(tabs): animation freeze when chaning tabs

* fix(tabs): poper item selecting programically

nativescript-core/ui/core/view-base/view-base.d.ts

@@ -474,7 +474,7 @@ export abstract class ViewBase extends Observable {
      * When returning true the callLoaded method will be run in setTimeout
      * Method is intended to be overridden by inheritors and used as "protected"
      */
-    _shouldDelayLoad(): boolean;
+    _shouldDelayLayout(): boolean;
 
     /**
      * @private

nativescript-core/ui/core/view-base/view-base.ts

@@ -561,12 +561,24 @@ export abstract class ViewBase extends Observable implements ViewBaseDefinition
         }
     }
 
+    private performLayout(currentRun = 0) {
+        // if there's an animation in progress we need to delay the layout
+        // we've added a guard of 5000 milliseconds execution
+        // to make sure that the layout will happen even if the animation haven't finished in 5 seconds
+        if (this._shouldDelayLayout() && currentRun < 100) {
+            setTimeout(() => this.performLayout(currentRun), currentRun);
+            currentRun++;
+        } else {
+            this.parent.requestLayout();
+        }
+    }
+
     @profile
     public requestLayout(): void {
         // Default implementation for non View instances (like TabViewItem).
         const parent = this.parent;
         if (parent) {
-            parent.requestLayout();
+            this.performLayout();
         }
     }
 
@@ -615,15 +627,11 @@ export abstract class ViewBase extends Observable implements ViewBaseDefinition
 
     public loadView(view: ViewBase): void {
         if (view && !view.isLoaded) {
-            if (this._shouldDelayLoad()) {
-                setTimeout(() => view.callLoaded());
-            } else {
-                view.callLoaded();
-            }
+            view.callLoaded();
         }
     }
 
-    public _shouldDelayLoad(): boolean {
+    public _shouldDelayLayout(): boolean {
         return false;
     }