Remove reliance on `out`'s value.

We should modify the `Abort` and `DebugPrint` `OutBAction`s to no longer rely on the value from `out`. Particularly, we should only rely on `out` to cause a VM exit and not on specifics of the mechanism. This will be helpful for the future when we add support other architectures that may not have `out` (e.g., ARM) and we need to change our doorbell mechanism. An alternate implementation for `Abort` and `DebugPrint` would be to pass a Hypervisor to the outb handler and retrieve registers values from the guest with info, which should be easy to do once #312 is merged.

> Note: We should also change the naming from `outb` to `out`.