src/vs/workbench/services/extensions/common/extensionsRegistry.ts/ExtensionPointUserDelta/_toSet
class ExtensionPointUserDelta:	private static _toSet<T>(arr: readonly IExtensionPointUser<T>[]): Set<string> {
		const result = new Set<string>();
		for (let i = 0, len = arr.length; i < len; i++) {
			result.add(ExtensionIdentifier.toKey(arr[i].description.identifier));
		}
		return result;
	}