use asByteArray _view_ where possible (optimization)

src/commonMain/kotlin/net/sergeych/utools/packing.kt

@@ -43,4 +43,4 @@ fun <T>pack(serializer: KSerializer<T>, element: T?): UByteArray =
 @Suppress("UNCHECKED_CAST")
 fun <T: Any?> unpack(serializer: KSerializer<T>, encoded: UByteArray): T =
     if (encoded.isEmpty()) null as T
-    else BipackDecoder.decode(encoded.toByteArray().toDataSource(),serializer)
+    else BipackDecoder.decode(encoded.asByteArray().toDataSource(),serializer)