add QueueStateSer

[lauralt]

Summary of the PR

Based on the design agreed here (and similar to what is already done in vm-superio), created a new crate, virtio-queue-ser, and added QueueStateSer. Once we have a fix for https://github.com/rust-vmm/vm-virtio/issues/143, this PR will probably need some updates, but high level it should remain the same. Marking this as draft until that.

Requirements

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

• [ ] All commits in this PR are signed (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.
• [ ] Any newly added unsafe code is properly documented.

[lauralt]

Since it is actually going to take some time to agree on the path forward with https://github.com/rust-vmm/vm-virtio/pull/150, I propose we review/merge this one before, and I can take care afterwards of any other changes to the state (if there will be any) that can be needed after the interface changes. Marking this as ready for review.