[JS IR BE] Implement kotlin.js.jsTypeOf as intrinsics

js/js.translator/testData/box/intrinsics/typeof.js

@@ -0,0 +1 @@
+var definedVariableX = 10;

js/js.translator/testData/box/intrinsics/typeof.kt

@@ -0,0 +1,12 @@
+// EXPECTED_REACHABLE_NODES: 1303
+external val definedVariableX: Int
+external val undefinedVariableX: Int
+
+fun box(): String {
+    if (jsTypeOf(definedVariableX) != "number") return "Fail 1"
+    if (jsTypeOf(js("definedVariableX")) != "number") return "Fail 2"
+    if (jsTypeOf(undefinedVariableX) != "undefined") return "Fail 3"
+    if (jsTypeOf(js("undefinedVariableX")) != "undefined") return "Fail 4"
+
+    return "OK"
+}