[Estuary] Skin integration of media import

[Montellese]

The following tasks must be completed to improve / finalize the skin integration of media import:

• [ ] Icon for Media importer add-on type
• [ ] Icon for Media sources setting tile
• [ ] Icon for All / Active / Inactive media providers
• [ ] Icon for media providers
• [ ] Icon for Add provider...
• [ ] Icon for media imports
• [ ] Icon for Add import...
• [x] Show Last synced: Never instead of Last synced:
• [ ] Change the look of disabled (if the media provider is not available) video items in the library