feat: initial support for native tab groups

[samfundev]

I was interested in tackling #1927. I didn't think it would be a good idea to remove Sidebery's groups so instead I made it migrate native groups to Sidebery's groups. The way it works is by creating a hidden group tab for each native group and then listens to native tab group events to keep things synchronized. Sorry, the code is still a bit rough since I'm not familiar with the code base and there's probably things I didn't handle. But hopefully this is enough to see if this is a good direction to go with implementing native tab group support.