media assets: add fix script to refresh metadata.

Add a script to go through every media asset and check the metadata
(width, height, duration, filesize, md5, EXIF metadata) and update it
if it's changed. This is necessary after upgrading ExifTool because the
metadata it returns may have changed.

app/models/media_asset.rb

@@ -78,6 +78,12 @@ class MediaAsset < ApplicationRecord
     end
 
     def open_file
+      open_file!
+    rescue
+      nil
+    end
+
+    def open_file!
       file = storage_service.open(file_path)
       frame_delays = media_asset.frame_delays if media_asset.is_ugoira?
       MediaFile.open(file, frame_delays: frame_delays, strict: false)