Make Task have type ActivityRecord children (55/n)

ActivityRecord now extends AppWindowToken and changing Task to have
type ActivityRecord children will make the Task level merging easier.

Bug: 80414790
Test: Existing tests pass
Change-Id: I331ffe054d942cc5dd58bff369fa890b130a45f4
diff --git a/services/tests/wmtests/src/com/android/server/wm/TaskStackTests.java b/services/tests/wmtests/src/com/android/server/wm/TaskStackTests.java
index 2eb6ea4..d045073 100644
--- a/services/tests/wmtests/src/com/android/server/wm/TaskStackTests.java
+++ b/services/tests/wmtests/src/com/android/server/wm/TaskStackTests.java
@@ -68,13 +68,13 @@
     public void testClosingAppDifferentStackOrientation() {
         final TaskStack stack = createTaskStackOnDisplay(mDisplayContent);
         final Task task1 = createTaskInStack(stack, 0 /* userId */);
-        AppWindowToken appWindowToken1 =
+        ActivityRecord appWindowToken1 =
                 WindowTestUtils.createTestAppWindowToken(mDisplayContent);
         task1.addChild(appWindowToken1, 0);
         appWindowToken1.setOrientation(SCREEN_ORIENTATION_LANDSCAPE);
 
         final Task task2 = createTaskInStack(stack, 1 /* userId */);
-        AppWindowToken appWindowToken2 =
+        ActivityRecord appWindowToken2 =
                 WindowTestUtils.createTestAppWindowToken(mDisplayContent);
         task2.addChild(appWindowToken2, 0);
         appWindowToken2.setOrientation(SCREEN_ORIENTATION_PORTRAIT);
@@ -88,13 +88,13 @@
     public void testMoveTaskToBackDifferentStackOrientation() {
         final TaskStack stack = createTaskStackOnDisplay(mDisplayContent);
         final Task task1 = createTaskInStack(stack, 0 /* userId */);
-        AppWindowToken appWindowToken1 =
+        ActivityRecord appWindowToken1 =
                 WindowTestUtils.createTestAppWindowToken(mDisplayContent);
         task1.addChild(appWindowToken1, 0);
         appWindowToken1.setOrientation(SCREEN_ORIENTATION_LANDSCAPE);
 
         final Task task2 = createTaskInStack(stack, 1 /* userId */);
-        AppWindowToken appWindowToken2 =
+        ActivityRecord appWindowToken2 =
                 WindowTestUtils.createTestAppWindowToken(mDisplayContent);
         task2.addChild(appWindowToken2, 0);
         appWindowToken2.setOrientation(SCREEN_ORIENTATION_PORTRAIT);