Fix JS source maps for delegates and backing fields

js/js.translator/testData/lineNumbers/delegation.kt

@@ -0,0 +1,21 @@
+class A :
+    I
+    by o
+
+interface I {
+    fun foo(): String
+
+    var bar: Int
+}
+
+val o = object : I {
+    override fun foo(): String = "foo"
+
+    override var bar: Int
+        get() = 23
+        set(value) {
+            println(value)
+        }
+}
+
+// LINES: 2 3 2 2 * 2 * 12 * 15 17