Adjust homepage styles and layouts

- Fine tune the header text size and position
- Fix the header overlapping problem on the homepage and collapsing
  toolbar pages when configuration changes by adding android:id.
- New AppBarScrollingViewBehavior for the homepage to avoid manually
  offsetting the IA
- Correct the formula of counting search box height

Test: robotest, manual
Fixes: 177967923
Fixes: 177968564
Change-Id: Id3ed44f4296fa2a19d6890b009d3881a5c140bbd

res/layout/search_bar.xml

@@ -23,7 +23,7 @@
     android:layout_marginTop="@dimen/search_bar_margin"
     android:layout_marginStart="@dimen/search_bar_margin"
     android:layout_marginEnd="@dimen/search_bar_margin"
-    android:layout_marginBottom="16dp"
+    android:layout_marginBottom="@dimen/search_bar_margin_bottom"
     app:layout_scrollFlags="scroll|enterAlways">
 
     <com.google.android.material.card.MaterialCardView

res/layout/settings_collapsing_base_layout.xml

@@ -23,6 +23,7 @@
     android:transitionGroup="true">
 
     <com.google.android.material.appbar.AppBarLayout
+        android:id="@+id/app_bar"
         android:layout_width="match_parent"
         android:layout_height="180dp"
         android:theme="@style/Theme.CollapsingToolbar.Settings">

res/layout/settings_homepage_container.xml

@@ -27,7 +27,7 @@
         android:id="@+id/main_content_scrollable_container"
         android:layout_width="match_parent"
         android:layout_height="match_parent"
-        app:layout_behavior="com.android.settings.widget.FloatingAppBarScrollingViewBehavior">
+        app:layout_behavior="com.android.settings.widget.HomepageAppBarScrollingViewBehavior">
 
         <LinearLayout
             android:id="@+id/homepage_container"
@@ -53,6 +53,7 @@
     </androidx.core.widget.NestedScrollView>
 
     <com.google.android.material.appbar.AppBarLayout
+        android:id="@+id/app_bar"
         android:layout_width="match_parent"
         android:layout_height="wrap_content"
         android:touchscreenBlocksFocus="false"