Sanitize names for backing fields and private declarations in JS BE

See KT-1816

js/js.translator/testData/box/delegateProperty/peculiarName.kt

@@ -0,0 +1,25 @@
+// EXPECTED_REACHABLE_NODES: 1006
+class X(private val x: String) {
+    operator fun getValue(thisRef: Any?, property: Any): String = x
+}
+
+class C {
+    @JsName("a") val `;`: String by X("foo")
+
+    private val `.`: String by X("bar")
+
+    private val `@`: String by X("baz")
+
+    fun bar(): String = `.`
+
+    fun baz(): String = `@`
+}
+
+fun box(): String {
+    val c = C()
+    if (c.`;` != "foo") return "fail1: ${c.`;`}"
+    if (c.bar() != "bar") return "fail2: ${c.bar()}"
+    if (c.baz() != "baz") return "fail3: ${c.baz()}"
+
+    return "OK"
+}