Reduce argon2 test runtime

Author: dipu-bd

test/argon2_test.dart

@@ -431,7 +431,7 @@ void main() {
           iterations: 3,
           parallelism: 2,
           memorySizeKB: 8192,
-          salt: List<int>.generate(0x3FFFFFF + 1, (i) => i),
+          salt: Uint8List(0x3FFFFFF + 1),
         ),
         throwsA(isA<ArgumentError>().having((e) => e.message, 'message',
             'The salt must be at most 67108863 bytes long')),
@@ -457,7 +457,7 @@ void main() {
           iterations: 3,
           parallelism: 2,
           memorySizeKB: 8192,
-          key: List<int>.generate(0x3FFFFFF + 1, (i) => i),
+          key: Uint8List(0x3FFFFFF + 1),
         ),
         throwsA(isA<ArgumentError>().having((e) => e.message, 'message',
             'The key must be at most 67108863 bytes long')),