CI: run cargo doc

[alyssais]

Summary of the PR

Link: #877 (comment)

Requirements

Before submitting your PR, please make sure you addressed the following
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• All commits in this PR have Signed-Off-By trailers (with
  git commit -s), and the commit message has max 60 characters for the
  summary and max 75 characters for each description line.
• All added/changed functionality has a corresponding unit/integration
  test.
• All added/changed public-facing functionality has entries in the "Upcoming
  Release" section of CHANGELOG.md (if no such section exists, please create one).
• Any newly added unsafe code is properly documented.

[stefano-garzarella]

@roypat @epilys @RuoqingHe do you think we should add something similar also in https://github.com/rust-vmm/rust-vmm-ci/blob/main/.buildkite/test_description.json ?

[roypat]

@roypat @epilys @RuoqingHe do you think we should add something similar also in rust-vmm/rust-vmm-ci@main/.buildkite/test_description.json ?

Yes, I think we should. crates.io automatically publishes our documentation to docs.rs, and if cargo doc doesnt work, that might limit discoverability of our crates

[alyssais]

Should I keep going with this PR, or is the idea that it'll be entirely handled in rust-vmm-ci?

[stefano-garzarella]

@alyssais unfortunately here in vhost-device we don't use the rust-vmm-ci pipeline, because we customized it, so we need to do in both. Thanks for the effort!

[alyssais]

Ah, I guess I actually need to fix the staging devices first!

[stefano-garzarella]

@alyssais I just rebased this on main since we merged #880
Do you plan to update also https://github.com/rust-vmm/rust-vmm-ci/blob/main/.buildkite/test_description.json ?

@epilys @stsquad @vireshk PTAL!

[alyssais]

I should be able to