Add pending extension indicator to extension panel

[alexeyre]

Summary

Add a marker to added extensions that have been installed but are yet to be enabled in the session.

Type of Change

• [x] Feature
• [ ] Bug fix
• [ ] Refactor / Code quality
• [ ] Performance improvement
• [ ] Documentation
• [ ] Tests
• [ ] Security fix
• [ ] Build / Release
• [ ] Other (specify below)

Testing

Manually tested by adding an extension from the goose extension library via the deeplink.

Related Issues

Relates to #5473

Screenshots/Demos (for UX changes)

Before:

After: