[PM-22380] Enable NRT for some Core project files (#5912)

* Enable NRT for Core/Jobs files

* Enable NRT for Core/HostedServices files

* Enable NRT for Core/Exceptions files

* Enable NRT for Core/NotificationHub files

---------

Co-authored-by: Bernd Schoolmann <mail@quexten.com>

src/Core/Jobs/BaseJob.cs

@@ -3,6 +3,8 @@ using Quartz;
 
 namespace Bit.Core.Jobs;
 
+#nullable enable
+
 public abstract class BaseJob : IJob
 {
     protected readonly ILogger _logger;