FIR checker: report nullable/non-class LHS of class literals

compiler/testData/diagnostics/tests/classLiteral/nonClassesOnLHS.fir.kt

@@ -2,11 +2,11 @@
 
 class A
 
-val a1 = A?::class
-val a2 = A??::class
+val a1 = <!NULLABLE_TYPE_IN_CLASS_LITERAL_LHS!>A?::class<!>
+val a2 = <!NULLABLE_TYPE_IN_CLASS_LITERAL_LHS!>A??::class<!>
 
-val l1 = List<String>?::class
-val l2 = List?::class
+val l1 = <!NULLABLE_TYPE_IN_CLASS_LITERAL_LHS!>List<String>?::class<!>
+val l2 = <!NULLABLE_TYPE_IN_CLASS_LITERAL_LHS!>List?::class<!>
 
 fun <T : Any> foo() {
     val t1 = <!OTHER_ERROR!>T<!>::class