Filter offline devices

Currently the device view shows all configured devices, whether online or offline. In some situations, devs might not want to see offline devices. We should add a setting to "hide offline devices", which should be enabled by default (i.e. the default behavior is that offline devices aren't visible).

This setting should be a user/workspace setting like the other ones, and we'll add a UI entry in the dropdown to toggle this visibility.

(While you're in there, also add a toggle for "show/hide dev devices" that is tied to the existing setting).

So defaults:

• offline devices are hidden
• non-dev devices are hidden