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/configStore/ConfigStore.java

@@ -5,6 +5,8 @@
 
 package com.wireguard.android.configStore;
 
+import com.wireguard.util.NonNullForAll;
+
 import com.wireguard.config.Config;
 
 import java.util.Set;
@@ -13,6 +15,7 @@ import java.util.Set;
  * Interface for persistent storage providers for WireGuard configurations.
  */
 
+@NonNullForAll
 public interface ConfigStore {
     /**
      * Create a persistent tunnel, which must have a unique name within the persistent storage

ui/src/main/java/com/wireguard/android/configStore/FileConfigStore.java

@@ -5,6 +5,8 @@
 
 package com.wireguard.android.configStore;
 
+import com.wireguard.util.NonNullForAll;
+
 import android.content.Context;
 import android.util.Log;
 
@@ -27,6 +29,7 @@ import java9.util.stream.Stream;
  * Configuration store that uses a {@code wg-quick}-style file for each configured tunnel.
  */
 
+@NonNullForAll
 public final class FileConfigStore implements ConfigStore {
     private static final String TAG = "WireGuard/" + FileConfigStore.class.getSimpleName();