Change importing rules for objects:

Allow importing classes from object, prohibit import-on-demand from objects
It's unclear what import-on-demand from object should mean so we prohibit it for now

compiler/testData/diagnostics/tests/imports/StarImportFromObject.kt

@@ -0,0 +1,47 @@
+package a
+
+import a.A.*
+import a.A.C
+import a.A.<!CANNOT_IMPORT_ON_DEMAND_FROM_SINGLETON!>C<!>.*
+import a.A.<!CANNOT_IMPORT_ON_DEMAND_FROM_SINGLETON!>D<!>.*
+import a.A.<!CANNOT_IMPORT_ON_DEMAND_FROM_SINGLETON!>C<!>.*
+import a.A.C.G
+import a.A.E.<!CANNOT_IMPORT_ON_DEMAND_FROM_SINGLETON!>J<!>.*
+import a.A.<!CANNOT_IMPORT_ON_DEMAND_FROM_SINGLETON!>CO<!>.*
+import a.A.CO
+
+import a.B.C.*
+import a.B.C.<!CANNOT_IMPORT_ON_DEMAND_FROM_SINGLETON!>A<!>.*
+import a.B.C.<!CANNOT_IMPORT_ON_DEMAND_FROM_SINGLETON!>D<!>.*
+
+import a.E.*
+import a.E.E1
+import a.E.<!CANNOT_IMPORT_ON_DEMAND_FROM_SINGLETON!>E2<!>.*
+
+class A {
+    object C {
+        object G
+    }
+    object D {
+
+    }
+
+    class E {
+        object J
+    }
+
+    class object CO {
+        object H
+    }
+}
+
+enum class E {
+    E1 E2
+}
+
+object B {
+    class C {
+        object A
+        object D
+    }
+}