feat: use vendoring step in Rust pure build

[zmitchell]

Note: the pure build will fail until flox/flox#3250 is solved.

This adds an impure build to vendor dependencies that can later be used in the Rust pure build. Creating the vendored dependencies is easy, but using the dependencies in the build requires creating a config file for Cargo to read. Cargo reads some environment variables at runtime, just not these variables in particular.

[ysndr]

I pushed a change to use the --config to pass an additional config file with the vendor data.
I think that fits better into the workflow of users that already hava a .cargo/config.toml where it becomes a bit annoying to merge a hand written toml back in to.
cargo --config <file> should instead overlay/add to the existing config leaving other config options in place.

It would have been nice if we could use the config generated by cargo vendor directly, but that refers to $out which for impure builds is not the same as ${deps} accessed by a consuming build :/

[dcarley]

I've used prefixed names for the Go and Ruby projects that the intermediate packages and store paths have more recognisable names when switching between projects in this repo.

Suggested change

	[build.deps]
	[build.quotes-app-rs-deps]

[dcarley]

LGTM and passing tests. Do think we should rename the build before merging though.

[ysndr]

renamed the deps build for consistency