Request option to not expand top-level directories

<!-- ⚠️⚠️ Do Not Delete This! feature_request_template ⚠️⚠️ --> <!-- Please read our Rules of Conduct: https://opensource.microsoft.com/codeofconduct/ --> <!-- Please search existing issues to avoid creating duplicates. --> <!-- Describe the feature you'd like. --> I have created a file system provider for a database and each time I log in and display the "directories" it goes through the `readDirectory()` step and fills the list. I'd prefer to have the directory start out collapsed and wait till the user expands it to populate the entries. This is different from #134665 in that I want it to be collapsed the first time (not on re-open). This is different from #87956 in that I'm not selecting a file. I'd like an API in FileSystemProvider to specify that a directory starts collapsed. The second choice would be a configuration option. Thanks!