FirSupertypesChecker: implement six more diagnostics

compiler/fir/analysis-tests/testData/resolve/overrides/supertypeGenericsComplex.fir.txt

@@ -1,5 +1,5 @@
 FILE: supertypeGenericsComplex.kt
-    public final class Out<out T> : R|kotlin/Any| {
+    public open class Out<out T> : R|kotlin/Any| {
         public constructor<out T>(): R|Out<T>| {
             super<R|kotlin/Any|>()
         }

compiler/fir/analysis-tests/testData/resolve/overrides/supertypeGenericsComplex.kt

@@ -1,4 +1,4 @@
-class Out<out T>
+open class Out<out T>
 
 interface X : <!INTERFACE_WITH_SUPERCLASS!>Out<String><!>