Enable Resolve v2 for workspace

[TheNeikos]

The v2 resolver allows for more fine-grained inclusion of dependency
features. Previously dev-dependency features got merged with 'normal'
dependency features. This may not always be desirable.

For more information see
https://doc.rust-lang.org/edition-guide/rust-2021/default-cargo-resolver.html

Types of changes

What types of changes does your code introduce to thin-edge.io?
Put an x in the boxes that apply

• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Improvement (general improvements like code refactoring that doesn't explicitly fix a bug or add any new functionality)
• Documentation Update (if none of the other choices apply)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

Further comments

This should be a non-breaking change as, as far as I could tell no crates had 'hidden' feature dependencies. However, since it is the default since the 2021 edition it makes sense to enable it now so as to reduce potential future workload.

[makr11st]

As per docs you provided the resolver = 2 is an implied as long as we use edtion = 2021 which we do.

[didier-wenzek]

Okay - even if this seems to be already the default since we are using edition = "2021".

[TheNeikos]

As per docs you provided the resolver = 2 is an implied as long as we use edtion = 2021 which we do.

That's what I expected as well, but:

From https://doc.rust-lang.org/edition-guide/rust-2021/default-cargo-resolver.html

The resolver is a global setting for a workspace, and the setting is ignored in dependencies. The setting is only honored for the top-level package of the workspace. If you are using a virtual workspace, you will still need to explicitly set the resolver field in the [workspace] definition if you want to opt-in to the new resolver.

There is an open issue about it: rust-lang/cargo#5784