Focus running task in overview grid

- calculateTaskSize now returns the Rect for focused task
- Introduced calculateGridTaskSize for non-focused task, and translate non-focused tasks to fit the grid
- As Task Rect is now vertically centered, removed ClearAllButton's grid vertical translation
- When ClearAllButton is not shown (e.g. quickswitch), make sure ClearAllButton's scroll won't be used when page snapping. This happens when page scrolls are translated so they're negative.
- Added back ActionsView when task is focused below the TaskView, which become invisible as you scroll
- In Modal state, move the ActionsView down so it won't cover the TaskView

Bug: 175939487
Test: manual
Change-Id: Idfa94a51f856418adc0503cf04211dcb4b1814fe
diff --git a/quickstep/overview_ui_overrides/res/layout/overview_actions_container.xml b/quickstep/overview_ui_overrides/res/layout/overview_actions_container.xml
index 1da25e7..b652252 100644
--- a/quickstep/overview_ui_overrides/res/layout/overview_actions_container.xml
+++ b/quickstep/overview_ui_overrides/res/layout/overview_actions_container.xml
@@ -14,10 +14,11 @@
      See the License for the specific language governing permissions and
      limitations under the License.
 -->
+<!-- NOTE! don't add dimensions for margins / gravity to root view in this file, they need to be
+     loaded at runtime. -->
 <com.android.quickstep.views.OverviewActionsView xmlns:android="http://schemas.android.com/apk/res/android"
     android:layout_width="match_parent"
-    android:layout_height="wrap_content"
-    android:layout_gravity="center_horizontal|bottom">
+    android:layout_height="wrap_content">
 
     <LinearLayout
         android:id="@+id/action_buttons"