Patch bip39 to use native crypto lib pbkdf2

[andrepimenta]

Description

This PR improves/fixes the android startup time by making bip39 use a native version of pbkdf2.

First it was needed to add a synchronous pbkdf2 function on the library react native aes crypto. Not doing so would make us have to change a lot of logic that uses bip39. So this was introduced on react-native-aes-crypto-lib:
Android side:

@ReactMethod(isBlockingSynchronousMethod = true)
	public String pbkdf2Sync(String pwd, String salt, Integer cost, Integer length)
	throws NoSuchAlgorithmException, InvalidKeySpecException, UnsupportedEncodingException
	{
        	String strs = pbkdf2(pwd, salt, cost, length);
			return strs;
    }

iOS side:

RCT_EXPORT_BLOCKING_SYNCHRONOUS_METHOD(pbkdf2Sync:(NSString *)password salt:(NSString *)salt
                  cost:(NSInteger)cost length:(NSInteger)length){
	
	return [AesCrypt pbkdf2:password salt:salt cost:cost length:length];
}

And then on bip39:

  // Bellow is the native equivalent of pbkdf2(mnemonicBuffer, saltBuffer, 2048, 64, 'sha512')

  const seed = Aes.pbkdf2Sync(mnemonicBuffer.toString('utf8'), saltBuffer.toString('utf8'), 2048, 512);
  const seedBuffer = global.Buffer.from(seed, "hex")

[estebanmino]

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