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/crypto/KeyFormatException.java

@@ -5,11 +5,14 @@
 
 package com.wireguard.crypto;
 
+import com.wireguard.util.NonNullForAll;
+
 /**
  * An exception thrown when attempting to parse an invalid key (too short, too long, or byte
  * data inappropriate for the format). The format being parsed can be accessed with the
  * {@link #getFormat} method.
  */
+@NonNullForAll
 public final class KeyFormatException extends Exception {
     private final Key.Format format;
     private final Type type;