Vscode: Explore improvements to welcome pages

[misolori]

This meta issue is to track the various work items related to the welcome page. The main goal is to improve our welcome page for new and existing users while also providing meaningful updates relating to extensions and product updates.

Issues

• [ ] First run user onboarding #106717
• [ ] Welcome page explorations https://github.com/microsoft/vscode/issues/63152
• [ ] What's new https://github.com/microsoft/vscode/issues/102139

[yangfansun]

we don't need welcome page!