global: get rid of nonnull gradle hack

Hacking things up via gradle is not right, and package-info.java poses
problems with two modules, so instead we just apply it manually to every
class.

Remember to add this to new classes!

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

ui/src/main/java/com/wireguard/android/model/ApplicationData.java

@@ -5,6 +5,8 @@
 
 package com.wireguard.android.model;
 
+import com.wireguard.util.NonNullForAll;
+
 import androidx.databinding.BaseObservable;
 import androidx.databinding.Bindable;
 import android.graphics.drawable.Drawable;
@@ -12,6 +14,7 @@ import android.graphics.drawable.Drawable;
 import com.wireguard.android.BR;
 import com.wireguard.util.Keyed;
 
+@NonNullForAll
 public class ApplicationData extends BaseObservable implements Keyed<String> {
     private final Drawable icon;
     private final String name;

ui/src/main/java/com/wireguard/android/model/ObservableTunnel.java

@@ -5,6 +5,8 @@
 
 package com.wireguard.android.model;
 
+import com.wireguard.util.NonNullForAll;
+
 import androidx.databinding.BaseObservable;
 import androidx.databinding.Bindable;
 import androidx.annotation.Nullable;
@@ -23,6 +25,7 @@ import java9.util.concurrent.CompletionStage;
  * Encapsulates the volatile and nonvolatile state of a WireGuard tunnel.
  */
 
+@NonNullForAll
 public class ObservableTunnel extends BaseObservable implements Keyed<String>, Tunnel {
     private final TunnelManager manager;
     @Nullable private Config config;

ui/src/main/java/com/wireguard/android/model/TunnelManager.java

@@ -5,6 +5,8 @@
 
 package com.wireguard.android.model;
 
+import com.wireguard.util.NonNullForAll;
+
 import android.content.BroadcastReceiver;
 import android.content.Context;
 import android.content.Intent;
@@ -39,6 +41,7 @@ import java9.util.stream.StreamSupport;
  * Maintains and mediates changes to the set of available WireGuard tunnels,
  */
 
+@NonNullForAll
 public final class TunnelManager extends BaseObservable {
     private static final Comparator<String> COMPARATOR = Comparators.<String>thenComparing(
             String.CASE_INSENSITIVE_ORDER, Comparators.naturalOrder());