Use insiders bits when running tests (#134578)

These tests run before the content for the webview is published. To work around this, we use previously published bits inside the tests. These only exist on insiders, not stable, so update the `webviewExternalEndpoint` always use insider when running the tests

src/vs/workbench/services/environment/browser/environmentService.ts

@@ -234,9 +234,10 @@ export class BrowserWorkbenchEnvironmentService implements IWorkbenchEnvironment
 			|| this.productService.webviewContentExternalBaseUrlTemplate
 			|| 'https://{{uuid}}.vscode-webview.net/{{quality}}/{{commit}}/out/vs/workbench/contrib/webview/browser/pre/';
 
+		const webviewExternalEndpointCommit = this.payload?.get('webviewExternalEndpointCommit');
 		return endpoint
-			.replace('{{commit}}', this.payload?.get('webviewExternalEndpointCommit') ?? this.productService.commit ?? '5f19eee5dc9588ca96192f89587b5878b7d7180d')
-			.replace('{{quality}}', this.productService.quality || 'insider');
+			.replace('{{commit}}', webviewExternalEndpointCommit ?? this.productService.commit ?? '5f19eee5dc9588ca96192f89587b5878b7d7180d')
+			.replace('{{quality}}', (webviewExternalEndpointCommit ? 'insider' : this.productService.quality) ?? 'insider');
 	}
 
 	@memoize