Exclude System events from ones that prohibits persistent objects changes

there might be scenarios when we might need to change registries even
in controversial scenarios

Author: alex-kulakov

Orm/Xtensive.Orm/Orm/Session.Persist.cs

@@ -210,8 +210,9 @@ private async ValueTask Persist(PersistReason reason, bool isAsync, Cancellation
             }
           }
         }
+
+        SystemEvents.NotifyPersisted();
         using (PreventRegistryChanges()) {
-          SystemEvents.NotifyPersisted();
           Events.NotifyPersisted();
         }
       }

Orm/Xtensive.Orm/Orm/Session.Transactions.cs

@@ -259,8 +259,8 @@ internal async ValueTask CommitTransaction(Transaction transaction, bool isAsync
 
       ValidationContext.Validate(ValidationReason.Commit);
 
+      SystemEvents.NotifyTransactionCommitting(transaction);
       using (PreventRegistryChanges()) {
-        SystemEvents.NotifyTransactionCommitting(transaction);
         Events.NotifyTransactionCommitting(transaction);
       }
 
@@ -373,8 +373,8 @@ internal void CompleteTransaction(Transaction transaction)
             OrmLog.Debug(nameof(Strings.LogSessionXCommittedTransaction), this);
           }
 
+          SystemEvents.NotifyTransactionCommitted(transaction);
           using (PreventRegistryChanges()) {
-            SystemEvents.NotifyTransactionCommitted(transaction);
             Events.NotifyTransactionCommitted(transaction);
           }
           break;
@@ -383,8 +383,8 @@ internal void CompleteTransaction(Transaction transaction)
             OrmLog.Debug(nameof(Strings.LogSessionXRolledBackTransaction), this);
           }
 
+          SystemEvents.NotifyTransactionRollbacked(transaction);
           using (PreventRegistryChanges()) {
-            SystemEvents.NotifyTransactionRollbacked(transaction);
             Events.NotifyTransactionRollbacked(transaction);
           }
           break;