refactor movie library scanners (#761)

* catch health check cancellation

* local library scanner cleanup

* emby and jf library scanner cleanup

* rework emby movie library scanner

* refactor emby movie library scanner

* refactor jellyfin movie library scanner

* clear etag until after new media has been processed

* refactor plex movie library scanner

* update changelog

ErsatzTV.Core/Interfaces/Emby/IEmbyMovieLibraryScanner.cs

@@ -9,5 +9,6 @@ public interface IEmbyMovieLibraryScanner
         string apiKey,
         EmbyLibrary library,
         string ffmpegPath,
-        string ffprobePath);
+        string ffprobePath,
+        CancellationToken cancellationToken);
 }

ErsatzTV.Core/Interfaces/Emby/IEmbyTelevisionLibraryScanner.cs

@@ -9,5 +9,6 @@ public interface IEmbyTelevisionLibraryScanner
         string apiKey,
         EmbyLibrary library,
         string ffmpegPath,
-        string ffprobePath);
+        string ffprobePath,
+        CancellationToken cancellationToken);
 }