FindFIles2 can stall forever with virtual file system with no search provider

[mjbvz]

For #313281

1. Install Joh's memfs extension
2. Close all workspace
3. Run Memfs: setup workspace and then memfs: create files
4. Try doing a call to vscode.findFiles2 with any args

Bug
This call stalls forever

It seems to be stuck waiting for a search provider to be registered, but this will never happen