Target WSL 2 instead of Vagrant for Windows

[lukateras]

Microsoft is releasing WSL 2, which will essentially be a very lightweight Linux VM shipped with Windows and maintained by Microsoft.

Relevant updates:

• May 6: https://devblogs.microsoft.com/commandline/announcing-wsl-2/
• June 12: https://devblogs.microsoft.com/commandline/wsl-2-is-now-available-in-windows-insiders/

It should be a faster/more convenient/better supported target for Windows users than Vagrant.

it will also be compatible with Nix, and it might even be good enough for that to be the only Windows support.

This is a bit of heads up, because AFAIK it has not been rolled to all users just yet, but it would be nice to know if that's something we should plan for in the future (in particular, this is tangentially related to my cross-compilation work).

If you have concerns about Nix cache requiring warmup, we have https://holo.cachix.org and can integrate that into holochain-rust CI to push artifacts as part of pipeline. End users and/or developers will be able to run $ cachix use holo in order to leverage that binary cache.

cc @thedavidmeister

[thedavidmeister]

i have a windows machine, i can test whatever

i do have concerns re: nix cache warmup but also note that Vagrant is a giant download anyway (3GB+) so it's not particularly fast either