JS: fix remaining tests. Suppress extensionFromTopLevelUnitOneStringArg.kt, use another approach to check whether object's property accessed via this

js/js.translator/testData/box/propertyAccess/privatePropertyAccessFromMethod.kt

@@ -1,18 +1,13 @@
+// ONLY_THIS_QUALIFIED_REFERENCES: foo_qltb3l$
+
 package foo
 
 object A {
     private val foo = 23
 
     fun bar(): Int {
-        // Erase object so that we ensure that access to 'foo' property is performed via 'this'
-        // It's no crucial from runtime standpoind, but JS code looks more concise and natural this way.
-        erase()
         return foo
     }
-
-    fun erase() {
-        js("_.foo.A = null")
-    }
 }
 
 fun box(): String {