Do this by:
- Removing more instances of `LockRefPtr` and `NonnullLockRefPtr`.
- Using better names of construction methods (i.e. `create` instead of
`try_create`).
- Only returning `NonnullRefPtr` on the `Device::try_create_device`
method.
- Removing a version of the `Device::try_create_device` method that
called `DeviceType::try_create(forward<Args>(args)...)`, which was
only used in a construction point in a VirtIO driver which now doesn't
need this anymore.
3edc6ae0d6