JS: fix identifier generation in delegate constructor calls

See KT-21093

compiler/testData/codegen/box/classes/delegateConstructorCallWithKeywords.kt

@@ -0,0 +1,30 @@
+open class A(val x: String) {
+    constructor(`in`: String, y: String) : this(`in` + y)
+
+    constructor(`in`: Int = 23) : this(`in`.toString())
+}
+
+class B(`in`: String) : A(`in`)
+
+class C : A {
+    constructor(`in`: String) : super(`in`)
+}
+
+fun box(): String {
+    val a1 = A("a", "b")
+    if (a1.x != "ab") return "fail1: ${a1.x}"
+
+    val a2 = A(42)
+    if (a2.x != "42") return "fail2: ${a2.x}"
+
+    val a3 = A()
+    if (a3.x != "23") return "fail3: ${a3.x}"
+
+    val b = B("q")
+    if (b.x != "q") return "fail4: ${b.x}"
+
+    val c = C("w")
+    if (c.x != "w") return "fail5: ${c.x}"
+
+    return "OK"
+}