add ExtHostFileSystemInfo which knows what schemes are reserved and which are used, https://github.com/microsoft/vscode/issues/91697

src/vs/workbench/api/common/extHostFileSystemInfo.ts

@@ -0,0 +1,35 @@
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the MIT License. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+
+import { Schemas } from 'vs/base/common/network';
+import { createDecorator } from 'vs/platform/instantiation/common/instantiation';
+import { ExtHostFileSystemInfoShape } from 'vs/workbench/api/common/extHost.protocol';
+
+export class ExtHostFileSystemInfo implements ExtHostFileSystemInfoShape {
+
+	declare readonly _serviceBrand: undefined;
+
+	private readonly _systemSchemes = new Set(Object.keys(Schemas));
+	private readonly _providerInfo = new Map<string, number>();
+
+	$acceptProviderInfos(scheme: string, capabilities: number | null): void {
+		if (capabilities === null) {
+			this._providerInfo.delete(scheme);
+		} else {
+			this._providerInfo.set(scheme, capabilities);
+		}
+	}
+
+	isFreeScheme(scheme: string): boolean {
+		return !this._providerInfo.has(scheme) && !this._systemSchemes.has(scheme);
+	}
+
+	getCapabilities(scheme: string): number | undefined {
+		return this._providerInfo.get(scheme);
+	}
+}
+
+export interface IExtHostFileSystemInfo extends ExtHostFileSystemInfo { }
+export const IExtHostFileSystemInfo = createDecorator<IExtHostFileSystemInfo>('IExtHostFileSystemInfo');