test: Easier to test with minimal features
test: Easier to test with minimal features

PR #2979 reduced what dependencies we push on users and made us one step
closer to being able to test more with fewer features.  Looks like I
also need to update `clap_derive`.  I verified locally that #2976 fails
with this.

`clap_derive` still needs `env` because of examples / tests that use it.
I feel like moving `clap_derive`s tests out to `clap` would be the way
to fix this.

clap-rs/clap,clap-rs/clap,clap-rs/clap