ci: unleash-check is failing in master pipeline #9129
Description
At the time of writing, the unleash-check job has been failing probably since #8472 (CI job).
The immediate reason for that is enabling a new Cargo feature resolver shipped in Rust 1.51, while cargo-unleash couldn't parse the updated manifest file at that time due to not supporting new enough Cargo-the-library.
However, simply using an updated cargo-unleash (#8848) does not fix the problem on its own, due to other local changes made to the workspace in the meantime, while the CI job was red.
The check originally meant to verify that the current workspace is publishable and builds in isolation. However, in the meantime we introduced some backwards incompatible changes and it looks like this can have a cascade impact on the entire workspace but the full extent of required changes is not yet determined.
It's worth keeping in mind that in the future an innocuous change might have a big impact across the graph possibly requiring us to bump major version. This ties into the discussion on how we should manage crate versioning (e.g. #7634) in that case but the relevant discussion should probably be had elsewhere.