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/Curve25519.java

@@ -6,6 +6,8 @@
 
 package com.wireguard.crypto;
 
+import com.wireguard.util.NonNullForAll;
+
 import androidx.annotation.Nullable;
 
 import java.util.Arrays;
@@ -25,6 +27,7 @@ import java.util.Arrays;
  * References: http://cr.yp.to/ecdh.html, RFC 7748
  */
 @SuppressWarnings({"MagicNumber", "NonConstantFieldWithUpperCaseName", "SuspiciousNameCombination"})
+@NonNullForAll
 public final class Curve25519 {
     // Numbers modulo 2^255 - 19 are broken up into ten 26-bit words.
     private static final int NUM_LIMBS_255BIT = 10;

tunnel/src/main/java/com/wireguard/crypto/Key.java

@@ -5,6 +5,8 @@
 
 package com.wireguard.crypto;
 
+import com.wireguard.util.NonNullForAll;
+
 import com.wireguard.crypto.KeyFormatException.Type;
 
 import java.security.MessageDigest;
@@ -18,6 +20,7 @@ import java.util.Arrays;
  * Instances of this class are immutable.
  */
 @SuppressWarnings("MagicNumber")
+@NonNullForAll
 public final class Key {
     private final byte[] key;
 

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;

tunnel/src/main/java/com/wireguard/crypto/KeyPair.java

@@ -5,11 +5,14 @@
 
 package com.wireguard.crypto;
 
+import com.wireguard.util.NonNullForAll;
+
 /**
  * Represents a Curve25519 key pair as used by WireGuard.
  * <p>
  * Instances of this class are immutable.
  */
+@NonNullForAll
 public class KeyPair {
     private final Key privateKey;
     private final Key publicKey;