Merge from vscode merge-base (#22780)

* Revert "Revert "Merge from vscode merge-base (#22769)" (#22779)"

This reverts commit 47a1745180.

* Fix notebook download task

* Remove done call from extensions-ci

extensions/markdown-language-features/server/src/util/limiter.ts

@@ -0,0 +1,67 @@
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the Source EULA. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+
+interface ILimitedTaskFactory<T> {
+	factory: ITask<Promise<T>>;
+	c: (value: T | Promise<T>) => void;
+	e: (error?: unknown) => void;
+}
+
+interface ITask<T> {
+	(): T;
+}
+
+/**
+ * A helper to queue N promises and run them all with a max degree of parallelism. The helper
+ * ensures that at any time no more than M promises are running at the same time.
+ *
+ * Taken from 'src/vs/base/common/async.ts'
+ */
+export class Limiter<T> {
+
+	private _size = 0;
+	private runningPromises: number;
+	private readonly maxDegreeOfParalellism: number;
+	private readonly outstandingPromises: ILimitedTaskFactory<T>[];
+
+	constructor(maxDegreeOfParalellism: number) {
+		this.maxDegreeOfParalellism = maxDegreeOfParalellism;
+		this.outstandingPromises = [];
+		this.runningPromises = 0;
+	}
+
+	get size(): number {
+		return this._size;
+	}
+
+	queue(factory: ITask<Promise<T>>): Promise<T> {
+		this._size++;
+
+		return new Promise<T>((c, e) => {
+			this.outstandingPromises.push({ factory, c, e });
+			this.consume();
+		});
+	}
+
+	private consume(): void {
+		while (this.outstandingPromises.length && this.runningPromises < this.maxDegreeOfParalellism) {
+			const iLimitedTask = this.outstandingPromises.shift()!;
+			this.runningPromises++;
+
+			const promise = iLimitedTask.factory();
+			promise.then(iLimitedTask.c, iLimitedTask.e);
+			promise.then(() => this.consumed(), () => this.consumed());
+		}
+	}
+
+	private consumed(): void {
+		this._size--;
+		this.runningPromises--;
+
+		if (this.outstandingPromises.length > 0) {
+			this.consume();
+		}
+	}
+}