Use unsafe cast instead of conversion that creates new array

multiplatform-crypto-api/src/commonMain/kotlin/com/ionspin/kotlin/crypto/hash/HashFunction.kt

@@ -40,6 +40,6 @@ interface Hash : HashFunction {
 }
 
 fun String.encodeToUByteArray() : UByteArray{
-    return encodeToByteArray().toUByteArray()
+    return encodeToByteArray().asUByteArray()
 }
 

multiplatform-crypto-api/src/commonMain/kotlin/com/ionspin/kotlin/crypto/util/StringUtil.kt

@@ -53,4 +53,4 @@ fun UByteArray.toHexString() : String {
             it.toString(16)
         }
     }
-}
+}