Kernel/Devices: Remove the DeviceManagement singleton

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.

Kernel/FileSystem/DevLoopFS/FileSystem.cpp

@@ -5,7 +5,7 @@
  */
 
 #include <Kernel/API/DeviceFileTypes.h>
-#include <Kernel/Devices/DeviceManagement.h>
+#include <Kernel/Devices/Device.h>
 #include <Kernel/Devices/Loop/LoopDevice.h>
 #include <Kernel/FileSystem/DevLoopFS/FileSystem.h>
 #include <Kernel/FileSystem/DevLoopFS/Inode.h>
@@ -58,7 +58,7 @@ ErrorOr<NonnullRefPtr<Inode>> DevLoopFS::get_inode(InodeIdentifier inode_id) con
         return *m_root_inode;
 
     unsigned loop_index = inode_index_to_loop_index(inode_id.index());
-    auto device = DeviceManagement::the().get_device(DeviceNodeType::Block, 20, loop_index);
+    auto device = Device::acquire_by_type_and_major_minor_numbers(DeviceNodeType::Block, 20, loop_index);
     VERIFY(device);
 
     auto& loop_device = static_cast<LoopDevice&>(*device);