For projects using version != 2021 and resolver = 2, the resolver
information needs to be kept or otherwise the dependency build might
fail.
---------
Co-authored-by: Ivan Petkov <ivanppetkov@gmail.com>
* Some tools may try to inspect crate types (e.g. wasm-pack) so it may
be useful to retain the attribute
* In general, the crate-type can influence the project's "structure" so
we should remain faithful to that
* Turns out the `required-features` attribute is only used from hiding
targets from cargo's selection (e.g. do not build unless feature is
enabled) and does not actually influence what features cargo will
enable/build for dependencies
