Network browsing: handle external media + save playback state

This is follow-up progress to !553 (closed).

Continuing Soomin's work with saving thumbnails and metadata, I fixed a bug about playback on SMB/UPnP files on the network. The causes of this problem are video on the SMB/UPnP doesn't store a media.duration.

One issue that I have is the current solution feels like a band-aid, and I'm still investigating why external media files won't load the proper data on VLCMLMedia, but I checked with VLCMetaData and it's correct, so that is pretty confusing for now. Simulator_Screen_Recording_-iPhone_14-_2023-06-13_at_195526_compressed

Closes #861 (closed)