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>

tunnel/src/main/java/com/wireguard/config/InetNetwork.java

@@ -5,6 +5,8 @@
 
 package com.wireguard.config;
 
+import com.wireguard.util.NonNullForAll;
+
 import java.net.Inet4Address;
 import java.net.InetAddress;
 
@@ -13,6 +15,7 @@ import java.net.InetAddress;
  * <p>
  * Instances of this class are immutable.
  */
+@NonNullForAll
 public final class InetNetwork {
     private final InetAddress address;
     private final int mask;