Wizard: show experimental new project wizard only by registry flag

idea/idea-new-project-wizard/src/org/jetbrains/kotlin/tools/projectWizard/wizard/NewProjectWizardModuleBuilder.kt

@@ -39,6 +39,8 @@ class NewProjectWizardModuleBuilder : ModuleBuilder() {
         const val MODULE_BUILDER_ID = "kotlin.newProjectWizard.builder"
     }
 
+    override fun isAvailable(): Boolean = NewProjectWizardService.isEnabled
+
     private var wizardContext: WizardContext? = null
 
     override fun getModuleType(): ModuleType<*> = NewProjectWizardModuleType()

idea/idea-new-project-wizard/src/org/jetbrains/kotlin/tools/projectWizard/wizard/NewProjectWizardService.kt

@@ -0,0 +1,13 @@
+/*
+ * Copyright 2010-2019 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
+ */
+
+package org.jetbrains.kotlin.tools.projectWizard.wizard
+
+import com.intellij.openapi.util.registry.Registry
+
+object NewProjectWizardService {
+    val isEnabled: Boolean
+        get() = Registry.`is`("kotlin.experimental.project.wizard", false)
+}