[KIE Sandbox] Can't open .bpmn files outside the active workspace in VSCode

How to reproduce:

• Open VSCode without an active workspace or a random workspace
• Open a .bpmn file outside the active workspace
• The editor should load indefinitely

Initial investigations:

• The error `EnvelopeBusMessageManager.ts:279 Uncaught (in promise) Error: fs.readdir is not a function` is shown in the console;
• The `fs.readdir` method is called in `VsCodeNodeResourceContentService.list`