Use ArgumentNullException.ThrowIfNull helper method

Did a simple search/replace on the whole repo (except the RSSDP project)
This reduces LOC and should improve performance (methods containing a throw statement don't get inlined)

```
if \((\w+) == null\)
\s+\{
\s+throw new ArgumentNullException\((.*)\);
\s+\}
```

```
ArgumentNullException.ThrowIfNull($1);
```

Jellyfin.Server.Implementations/Devices/DeviceManager.cs

@@ -201,10 +201,7 @@ namespace Jellyfin.Server.Implementations.Devices
         /// <inheritdoc />
         public bool CanAccessDevice(User user, string deviceId)
         {
-            if (user == null)
-            {
-                throw new ArgumentNullException(nameof(user));
-            }
+            ArgumentNullException.ThrowIfNull(user);
 
             if (string.IsNullOrEmpty(deviceId))
             {