decrypt: Double memory use

[IvanPizhenko]

It seems this method uses ByteArray as an input.

And here we use RAM twice.

val output = ByteArrayOutputStream()
decryptionStream.use { it.copyTo(output) }

@tomholub I think the current approach is enough to drop Node.js (I mean don't care about RAM). But it has performance issues for Android. We will have to improve that in the near future(upcoming releases).

Originally posted by @DenBond7 in #1216 (comment)