lints workflow : feature or crate selection

[huitseeker]

Documenting an issue encountered in lurk-lab/neptune#255, which is arguably the fault of the crate organization:

• the gbench crate (which is non-publish!) runs with the default opencl feature, which does not compile on some CI machines:
  https://github.com/lurk-lab/neptune/blob/main/gbench/Cargo.toml#L25
• the lint crate runs with workspace in the doc step of the job:
  https://github.com/lurk-lab/neptune/actions/runs/7294189991/job/19878612122?pr=255
  https://github.com/lurk-lab/ci-workflows/blob/96e567fa741858807c1de28bb4d8194291faecfb/.github/workflows/lints.yml#L49

Three ways to solve this:

• make the gbench feature non-default, just generate a runtime panic if neither of opencl nor cuda are active,
• allow excluding a crate from the doc test,
• allow excluding a feature (or running with default-deatures = false) from the doc test,