Plugin host onDidCreateFiles isn't fired when running Save As command

[msujew]

Bug Description:

I've noticed this while looking into #13687. The vscode.workspace.onDidCreateFiles event isn't fired when a new file is created in the workspace as part of a "Save As" operation.

Consumers (such as language servers) therefore aren't notified about these files.

Steps to Reproduce:

1. Set a breakpoint here.
2. Use the New File command.
3. Save the untitled resource.
4. The breakpoint isn't hit, the event doesn't fire.

Additional Information

• Theia Version: 1.49.0