[Wasm] Pass js stack value directly when replacing a wasm exception with JS one

In this case, we don't need to convert a value to and from wasm String.

libraries/stdlib/wasm/builtins/kotlin/Throwable.kt

@@ -22,7 +22,7 @@ public open class Throwable(open val message: String?, open val cause: kotlin.Th
 
     constructor() : this(null, null)
 
-    private val jsStack: ExternalInterfaceType = captureStackTrace()
+    internal val jsStack: ExternalInterfaceType = captureStackTrace()
 
     private var _stack: String? = null
     internal val stack: String