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.
This change has many improvements:
- We don't use `LockRefPtr` to hold instances of many base devices as
with the DeviceManagement class. Instead, we have a saner pattern of
holding them in a `NonnullRefPtr<T> const`, in a small-text footprint
class definition in the `Device.cpp` file.
- The awkwardness of using `::the()` each time we need to get references
to mostly-static objects (like the Event queue) in runtime is now gone
in the migration to using the `Device` class.
- Acquiring a device feel more obvious because we use now the Device
class for this method. The method name is improved as well.
We used to allocate major numbers quite randomly, with no common place
to look them up if needed.
This commit is changing that by placing all major number allocations
under a new C++ namespace, in the API/MajorNumberAllocation.h file.
We also add the foundations of what is needed before we can publish this
information (allocated numbers for block and char devices) to userspace.
It can be possible for a request to be blocked on another request, so
this patch allows us to send more requests even when a request is
already pending.
