MM-15021: Adding new builtin system schema for Guests (#10601)

* MM-15021: Adding new builtin system schema for Guests

* Fixing tests

* Setting properly the permissions

* Adding guests to sampledata

* Restrict more roles updates in the app layer for guests

* Adding comment to explain that permissions migration must go at the end

* Setting the default guest role for custom scheme during migration

* Fixing import and export

* Creating scheme guest roles on migration

* Fixing tests

* Fixing tests

* Fixing tests

web/web_test.go

@@ -70,8 +70,7 @@ func Setup() *TestHelper {
 	URL = fmt.Sprintf("http://localhost:%v", a.Srv.ListenAddr.Port)
 	ApiClient = model.NewAPIv4Client(URL)
 
-	a.DoAdvancedPermissionsMigration()
-	a.DoEmojisPermissionsMigration()
+	a.DoAppMigrations()
 
 	a.Srv.Store.MarkSystemRanUnitTests()