debug: only save when starting a new top-level session

Fixes https://github.com/microsoft/vscode-node-debug2/issues/257

src/vs/workbench/contrib/debug/browser/debugService.ts

@@ -270,7 +270,9 @@ export class DebugService implements IDebugService {
 		try {
 			// make sure to save all files and that the configuration is up to date
 			await this.extensionService.activateByEvent('onDebug');
-			await this.editorService.saveAll();
+			if (!options?.parentSession) {
+				await this.editorService.saveAll();
+			}
 			await this.configurationService.reloadConfiguration(launch ? launch.workspace : undefined);
 			await this.extensionService.whenInstalledExtensionsRegistered();