[Wasm] Rewrite lazy initialization without by lazy and lateinit to reduce overhead

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

@@ -24,13 +24,16 @@ public open class Throwable(open val message: String?, open val cause: kotlin.Th
 
     private val jsStack: ExternalInterfaceType = captureStackTrace()
 
-    private lateinit var _stack: String
+    private var _stack: String? = null
     internal val stack: String
         get() {
-            if (!::_stack.isInitialized) {
-                _stack = jsToKotlinStringAdapter(jsStack).removePrefix("Error\n")
+            var value = _stack
+            if (value == null) {
+                value = jsToKotlinStringAdapter(jsStack).removePrefix("Error\n")
+                _stack = value
             }
-            return _stack
+
+            return value
         }
 
     internal var suppressedExceptionsList: MutableList<Throwable>? = null

libraries/stdlib/wasm/internal/kotlin/wasm/internal/ExternalWrapper.kt

@@ -281,28 +281,40 @@ private fun getJsTrue(): JsBoolean =
 private fun getJsFalse(): JsBoolean =
     js("false")
 
-private lateinit var _jsEmptyString: JsString 
+private var _jsEmptyString: JsString? = null
 private val jsEmptyString: JsString
     get() {
-        if (!::_jsEmptyString.isInitialized)
-            _jsEmptyString = getJsEmptyString()
-        return _jsEmptyString
+        var value = _jsEmptyString
+        if (value == null) {
+            value = getJsEmptyString()
+            _jsEmptyString = value
+        }
+
+        return value
     }
 
-private lateinit var _jsTrue: JsBoolean
+private var _jsTrue: JsBoolean? = null
 private val jsTrue: JsBoolean
     get() {
-        if (!::_jsTrue.isInitialized)
-            _jsTrue = getJsTrue()
-        return _jsTrue
+        var value = _jsTrue
+        if (value == null) {
+            value = getJsTrue()
+            _jsTrue = value
+        }
+
+        return value
     }
 
-private lateinit var _jsFalse: JsBoolean
-private val jsFalse: JsBoolean 
+private var _jsFalse: JsBoolean? = null
+private val jsFalse: JsBoolean
     get() {
-        if (!::_jsFalse.isInitialized)
-            _jsFalse = getJsFalse()
-        return _jsFalse
+        var value = _jsFalse
+        if (value == null) {
+            value = getJsFalse()
+            _jsFalse = value
+        }
+
+        return value
     }
 
 internal fun numberToDoubleAdapter(x: Number): Double =