scanner refactoring and other cleanup (#1082)

* move subtitles provider into scanner

* move more stuff into scanner

* move nfo into scanner

* add scan subcommand

* fix a bunch of nfo build warnings

* more subcommands

* fix warnings

* cleanup logging

* remove unused code

* cleanup old ffmpeg stuff

* rename complex filter

* refactor wrapped segmenter

ErsatzTV.Core/Metadata/LocalFileSystem.cs

@@ -94,7 +94,7 @@ public class LocalFileSystem : ILocalFileSystem
 
     public IEnumerable<string> ListFiles(string folder, string searchPattern)
     {
-        if (Directory.Exists(folder))
+        if (folder is not null && Directory.Exists(folder))
         {
             try
             {