Add helper to run cargo windsock --cloud within docker for libc compatibility reasons

[rukai]

Previously I was trying to solve the windsock libc mismatch issue by moving windsock entirely into the cloud via ec2-cargo.
However once I got far enough into that approach to get things working I found it was too slow. Every time I rerun ec2-cargo I have to rebuild the world and the ec2 instance is fast but still slower than my local machine, so even incremental rebuilds are still slower.

So I looked for alternatives and settled on this approach:
Setup a long running docker instance that uses ubuntu 20.04 and run windsock --cloud from within there.
I had previously tried cross which is a similar solution but hit so many problems that I gave up on docker entirely.
However the problem was just that cross's abstractions prevented me from running cargo windsock from within the instance.
Once I tried docker directly I found a fairly straightforward solution.

I've left optimizing the shotover project directory copy for a follow up PR, I would like to get this checked in so I can at least personally run windsock on aws again.

I might end up rolling back the ec2-cargo windsock functionality if it becomes a pain to maintain.
But it does still provide some value in that it lets us run windsock on aarch64.