Go backend

[zefhemel]

Implements #1549

Should be functionally equivalent (only had to drop the sync sub command which I hope nobody used or even knew about anyway).

Fun facts:

• Server builds (single binary) are now about ~7MB zipped vs ~30MB zipped with Deno

Docker builds will soon be available under the :v2-go tag.

Things to do after this is merged:

• Reconsider the whole repo code structure, it's a bit messy now
• Consider building the main docker images from Alpine rather than ubuntu, because there's no longer a glibc dependency (maybe offer two versions, e.g. -ubuntu and -alpine)

[PowerUser64]

Let's Go! 🚀 Feel free to let me know when this is functional and I can provide beta testing.

[zefhemel]

This is now ready for test @PowerUser64 you can build it yourself, or use the :v2-go docker tag. I've now switched to it on my own main instance and will test with it for a few days.