Add tokenization and context provider API types

- Implemented window delineation tests for indentation-based tokenization.
- Created tokenizer module with various tokenization strategies including TTokenizer and ApproximateTokenizer.
- Added type definitions for authentication parameters and code citation notifications.
- Introduced context provider API for extensions to supply additional context items to Copilot.
- Defined core types and schemas for position and range.
- Established status types for agent status management in IDEs.

completions-sample-code/extension/src/panelShared/utils.ts

@@ -0,0 +1,17 @@
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the MIT License. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+
+export function getNonce() {
+	let text = '';
+	const possible = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789';
+	for (let i = 0; i < 32; i++) {
+		text += possible.charAt(Math.floor(Math.random() * possible.length));
+	}
+	return text;
+}
+
+export function pluralize(count: number, noun: string, suffix = 's') {
+	return `${count} ${noun}${count !== 1 ? suffix : ''}`;
+}