workflow: clone cloud-hypervisor repo as public

workflow: clone cloud-hypervisor repo as public

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Before submitting your PR, please make sure you addressed the following requirements:

[x] 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.
[x] All added/changed functionality has a corresponding unit/integration test.
[x] All added/changed public-facing functionality has entries in the "Upcoming Release" section of CHANGELOG.md (if no such section exists, please create one).
[x] Any newly added unsafe code is properly documented.

rust-vmm / mshv