feat(frame): handle back navigation when common layout is used as a root element (#5608)

* test(e2e): update modal navigation app

Add layout as root.
Add show modal layout.

* chore(frame): move frame stack modifiers in a separate frame-stack module

* feat(frame): handle back navigation when using common layout as root element

tns-core-modules/ui/frame/frame-stack.ts

@@ -0,0 +1,50 @@
+// Types.
+import { FrameBase } from "./frame-common";
+
+export let frameStack: Array<FrameBase> = [];
+
+export function topmost(): FrameBase {
+    if (frameStack.length > 0) {
+        return frameStack[frameStack.length - 1];
+    }
+
+    return undefined;
+}
+
+export function _pushInFrameStack(frame: FrameBase): void {
+    if (frame._isInFrameStack && frameStack[frameStack.length - 1] === frame) {
+        return;
+    }
+
+    if (frame._isInFrameStack) {
+        const indexOfFrame = frameStack.indexOf(frame);
+        frameStack.splice(indexOfFrame, 1);
+    }
+
+    frameStack.push(frame);
+    frame._isInFrameStack = true;
+}
+
+export function _popFromFrameStack(frame: FrameBase): void {
+    if (!frame._isInFrameStack) {
+        return;
+    }
+
+    const top = topmost();
+    if (top !== frame) {
+        throw new Error("Cannot pop a Frame which is not at the top of the navigation stack.");
+    }
+
+    frameStack.pop();
+    frame._isInFrameStack = false;
+}
+
+export function _removeFromFrameStack(frame: FrameBase): void {
+    if (!frame._isInFrameStack) {
+        return;
+    }
+
+    const index = frameStack.indexOf(frame);
+    frameStack.splice(index, 1);
+    frame._isInFrameStack = false;
+}