Add AniDb Season ProviderId

[nalsai]

I updated getting metadata for seasons, however it currently doesn't make sense to do so because you can't get the SeasonProviderIds for episodes (there is no info.SeasonProviderIds) and therefore you can't get the correct episode metadata for season other than the main one, whose Id would also be in info.SeriesProviderIds. Therefore I commented it out and the only noticeable change this PR makes is adding the ProviderId for seasons.

Old behaviour:

• create empty MetadataResult
• get ProviderId
• ProviderId isn't set
  • --> return empty result created earlier
• if you set the ProviderId manually, it adds the metadata for that to the season, but the episodes have the metadata for the show independently of the season (doesn't make sense)

New behaviour:

• get ProviderId
• if ProviderId not set:
  • add ProviderId from show to the season (if it's season 1 or IgnoreSeason is true) and return
• code to get metadata is commented out because it currently doesn't make sense (but could be implemented in the future if SeasonProviderIds gets added to the EpisodeInfo class in jellyfin)
• return empty MetadataResult

Shokofin adds the ProviderId for seasons, and has support for different seasons, I believe. For better interoperability with plugins like jellyfin-ani-sync this plugin should add the ProviderId for seasons too.

[nalsai]

I will make a new PR when it's ready.