Support multiple `--bin` values in `cargo chef prepare`

[SupernaviX]

Hello!

I'm working on a workspace project where

1. some projects are apps which are meant to be bundled in docker images
2. some projects are libraries which are used by those apps
3. some projects are separate (e.g. a demo application) and shouldn't be involved in the docker build at all.

I'd really like to be able to build a recipe file which included all projects of types 1 and 2, but excluded 3. It looks like the prepare command accepts a --bin argument which would help with this, but you can only use that for a single project. I think it would serve my needs if you could pass more than one --bin, like you can with the build command.