Port most notebook model code over to be behind a service (#3068)

- Defines a new NotebookService in Azure Data Studio which will be used to interact with notebooks. Since notebooks can require per-file instantiation the provider is just used to create & track managers for a given URI.
- Inject this into notebook.component.ts and pass required parameters that'll be used to properly initialize a manger into the method. Actual initialization not done yet.
- Port over & recompile notebook model code
- Define most required APIs in sqlops.proposed.d.ts. In the future, these will be used by extensions to contribute their own providers.

src/sql/services/notebook/notebookServiceImpl.ts

@@ -0,0 +1,60 @@
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the Source EULA. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+
+'use strict';
+
+import { nb } from 'sqlops';
+import * as nls from 'vs/nls';
+import { INotebookService, INotebookManager, INotebookProvider } from 'sql/services/notebook/notebookService';
+import URI from 'vs/base/common/uri';
+
+export class NotebookService implements INotebookService {
+	_serviceBrand: any;
+
+	private _providers: Map<string, INotebookProvider> = new Map();
+	private _managers: Map<URI, INotebookManager> = new Map();
+
+	registerProvider(providerId: string, provider: INotebookProvider): void {
+		this._providers.set(providerId, provider);
+	}
+
+	unregisterProvider(providerId: string): void {
+		this._providers.delete(providerId);
+	}
+
+	public shutdown(): void {
+		this._managers.forEach(manager => {
+			if (manager.serverManager) {
+				// TODO should this thenable be awaited?
+				manager.serverManager.stopServer();
+			}
+		});
+	}
+
+	async getOrCreateNotebookManager(providerId: string, uri: URI): Promise<INotebookManager> {
+		if (!uri) {
+			throw new Error(nls.localize('notebookUriNotDefined', 'No URI was passed when creating a notebook manager'));
+		}
+		let manager = this._managers.get(uri);
+		if (!manager) {
+			manager = await this.doWithProvider(providerId, (provider) => provider.getNotebookManager(uri));
+			if (manager) {
+				this._managers.set(uri, manager);
+			}
+		}
+		return manager;
+	}
+
+	// PRIVATE HELPERS /////////////////////////////////////////////////////
+	private doWithProvider<T>(providerId: string, op: (provider: INotebookProvider) => Thenable<T>): Thenable<T> {
+		// Make sure the provider exists before attempting to retrieve accounts
+		let provider = this._providers.get(providerId);
+		if (!provider) {
+			return Promise.reject(new Error(nls.localize('notebookServiceNoProvider', 'Notebook provider does not exist'))).then();
+		}
+
+		return op(provider);
+	}
+}