FIR: implement checker for open members

Specifically,

1. NON_FINAL_MEMBER_IN_FINAL_CLASS
2. NON_FINAL_MEMBER_IN_OBJECT

compiler/fir/entrypoint/src/org/jetbrains/kotlin/fir/checkers/CommonDeclarationCheckers.kt

@@ -39,6 +39,7 @@ object CommonDeclarationCheckers : DeclarationCheckers() {
     override val classCheckers: Set<FirClassChecker> = setOf(
         FirOverrideChecker,
         FirThrowableSubclassChecker,
+        FirOpenMemberChecker,
     )
 
     override val regularClassCheckers: Set<FirRegularClassChecker> = setOf(