FirSupertypesChecker: implement six more diagnostics

compiler/testData/diagnostics/tests/imports/ImportObjectAndUseAsSupertype.fir.kt

@@ -1,19 +0,0 @@
-// FILE: a.kt
-
-package foo
-
-object Bar {
-    fun bar() {}
-}
-
-// FILE: b.kt
-
-package baz
-
-import foo.Bar
-
-class C: Bar
-
-fun test() {
-    Bar.bar()
-}

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

@@ -1,3 +1,4 @@
+// FIR_IDENTICAL
 // FILE: a.kt
 
 package foo

compiler/testData/diagnostics/tests/imports/PrivateClassReferencedError.fir.kt

@@ -11,4 +11,4 @@ package a
 
 import pack1.SomeClass.*
 
-private class X : <!EXPOSED_SUPER_CLASS, INVISIBLE_REFERENCE!>N<!>()
+private class X : <!EXPOSED_SUPER_CLASS, FINAL_SUPERTYPE, INVISIBLE_REFERENCE!>N<!>()