More work around isolating node imports (#6512)

* more work around isolating node imports

* rewrite query plan input

* fix hygiene errors

* fix tests

* address feedback

* remove welcome page changes

src/sql/platform/notebooks/common/outputRegistry.ts

@@ -0,0 +1,34 @@
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the Source EULA. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+
+import { Registry } from 'vs/platform/registry/common/platform';
+
+export const Extensions = {
+	CellComponentContributions: 'notebook.contributions.cells'
+};
+
+export interface ICellComponenetRegistry {
+	registerComponent(component: any): void;
+	getComponents(): Array<any>;
+}
+
+class CellComponenetRegistry implements ICellComponenetRegistry {
+	private components = new Array<any>();
+
+	registerComponent(component: any): void {
+		this.components.push(component);
+	}
+
+	getComponents(): any[] {
+		return this.components.slice();
+	}
+}
+
+const componentRegistry = new CellComponenetRegistry();
+Registry.add(Extensions.CellComponentContributions, componentRegistry);
+
+export function registerCellComponent(component: any): void {
+	componentRegistry.registerComponent(component);
+}