Fail fast for minimal-versions check

[joshka]

In RustCrypto/elliptic-curves#1039 (comment) we noted that the use of hack to test combinations can be overkill (and take a long time when there are lots of combinations - some combinations were as long as 15-30 minutes).

As an optimization, perhaps adding cargo test --all-features as an initial step to the workflow would be the right thing to do. If that fails, there there's enough information to get started on fixing the problem and running cargo-hack won't be all that helpful.

[newpavlov]

Note that you already can overwrite the default command by providing the stable-cmd variable. Adding cargo test --all-features by default could be a good addition though.

[joshka]

Good idea to push this upstream!

[newpavlov]

This will be fixed by cargo hack in a future release.