feat(Escaped Identifiers): add ability to use any symbol wrapped in back ticks.

js/js.translator/testData/box/escapedIdentifiers/dynamicEscapedField.kt

@@ -0,0 +1,11 @@
+// IGNORE_BACKEND: JS
+// !LANGUAGE: +JsAllowInvalidCharsIdentifiersEscaping
+
+package foo
+
+fun box(): String {
+    val a: dynamic = js("{ \"--invalid--property@\": 42 }")
+    assertEquals(42, a.`--invalid--property@`)
+
+    return "OK"
+}