support Kusion view in the primary sidebar view

## Feature Request

kusion VS Code Extension needs to support application/cluster/resources info/status view in the primary sidebar view.
When there are no kusion projects found, a welcome page is needed to guide users to create a new kusion project by binding the application source code repos with the corresponding infra code repo/paths.


ref:
- vscode views: https://code.visualstudio.com/api/ux-guidelines/views

Start with the VS Code Views UX guidelines linked in the issue and inspect the extension's existing sidebar and Kusion project entry points. Done means the primary sidebar shows application, cluster, and resource information/status, and no-project users see guidance for creating a project by binding application source and infrastructure repositories or paths.

Written by the indexing model from the issue text.