Support opening the Query Editor from outside (Portal, Fabric) using registerUriHandler

[sevoku]

We want to add "Open in VS Code" buttons to the Azure Portal and Fabric, for this we need to implement a handler using vscode.window.registerUriHandler (on activation) which will open the selected database/container in the Query Editor.

We also need to investigate whether we can navigate to the appropriate node in the resource tree (which might require changes to the Azure Resources extension)