This PR fixes a few issues related to `vc dev`.
1. Create a default `go.work` file in the cache dir when building the `vercel-dev-server-go` executable
2. Copy the existing `go.mod` file into the cache dir and update any "replace" relative paths
3. Split the "build" logic into separate functions for the legacy "main" package build and the `go.mod` build
Additionally, it fixes:
1. `vc build`: pass in `build.env` from `vercel.json`
2. Fix several tests to work with `vc dev` and `vc build`
Linear: https://linear.app/vercel/issue/VCCLI-638/vc-dev-go-builder-cant-resolve-workspace-dependencies
The user that reported the issue has tested this build and seems to fix their use case: https://github.com/vercel/vercel/issues/9393#issuecomment-1490726785.
