Pre-install VS Code extensions in desktop VS Code module

Extend the VS Code desktop module to automatically install the specified extensions and apply settings.

- Should accept the extension list as a parameter
- Should accept settings as input
- Should install the extension for the remote host
- Extend the existing [VSCode Desktop module](https://registry.coder.com/modules/coder/vscode-desktop) with this new feature

> [!NOTE]
> When a user connects to a Coder workspace for the first time, the extension and settings should be pre-installed and pre-applied.