FIR: implement diagnostics for qualifier as stand-alone expression case

compiler/testData/codegen/box/package/privateMembersInImportList.kt

@@ -1,3 +1,4 @@
+// IGNORE_BACKEND_FIR: JVM_IR
 package test
 
 import test.C.E1
@@ -16,6 +17,7 @@ class A {
     }
 
     fun test() {
+        // Note: FIR resolve this to test/C instead of test/A.B.C
         C
         D()
     }