ui: address new databinding requirements

Layouts in differing configurations must agree on their root tags, so we give
both copies of main_activity the same root ID, and adjust the check for
two-pane layout to simply test for nullability. This also changes the inset
dispatch code to use ViewCompat and WindowInsetsCompat since they will adjust
insets based on the SDK level allowing us to abstract away that concern.

Signed-off-by: Harsh Shandilya <me@msfjarvis.dev>

ui/src/main/res/layout-sw600dp/main_activity.xml

@@ -1,6 +1,7 @@
 <?xml version="1.0" encoding="utf-8"?>
 <androidx.coordinatorlayout.widget.CoordinatorLayout xmlns:android="http://schemas.android.com/apk/res/android"
     xmlns:tools="http://schemas.android.com/tools"
+    android:id="@+id/main_activity_container"
     android:layout_width="match_parent"
     android:layout_height="match_parent"
     tools:context=".activity.MainActivity">

ui/src/main/res/layout/main_activity.xml

@@ -1,7 +1,7 @@
 <?xml version="1.0" encoding="utf-8"?>
 <androidx.coordinatorlayout.widget.CoordinatorLayout xmlns:android="http://schemas.android.com/apk/res/android"
     xmlns:tools="http://schemas.android.com/tools"
-    android:id="@+id/master_detail_wrapper"
+    android:id="@+id/main_activity_container"
     android:layout_width="match_parent"
     android:layout_height="match_parent"
     android:fitsSystemWindows="true"