[Bug] Silent failure if USB is already connected in another tab

[laurensvalk]

Describe the bug Nothing appears to happen if you try to connect to USB if it is already connected in another tab. Even though the dialog does appear to work.

To reproduce Steps to reproduce the behavior:

• Connect with USB on one tab
• Have coffee
• Forget that Pybricks is already opened
• Try to connect, choose brick from Chrome dialog
• Be confused.

Expected behavior A toast to say that it is already connected in another tab. Just like we have a toast if you try to open a code file that is already opened in another tab.

I suppose can catch the Failed to claim interface error.