Creating vendor directories directly in srcs of go and rust packages so fixed output derivations won't be needed

[doronbehar]

I think we need to setup a CI system such as Mach-nix but for Go, Rust, and NodeJS. I tend to imagine it should be easier to create such systems for these ecosystems vs how hard it was for @DavHau to do it for Python. Because crates.io and and sum.golang.org are much more arranged then pypi.org .