Make Uhyve aware of process-wide limits

[n0toose]

By implementing limits, Uhyve could continue to function / not crash (or otherwise show any unexpected behavior) if a process-wide limit (e.g. amount of open file handles) is exhausted by a guest OS. This will become feasible (and somewhat trivial to implement) when #857 is merged.

See: https://gitlab.com/virtio-fs/virtiofsd/-/blob/main/src/limits.rs