Update to .NET 8

[Gauvino]

Updating arr* to .NET 8

• Sonarr: https://github.com/Sonarr/Sonarr/pull/6580
• Radarr: https://github.com/Radarr/Radarr/pull/9829
• Lidarr: https://github.com/Lidarr/Lidarr/pull/4767
• Readarr:
• Whisparr:
• Prowlarr: https://github.com/Prowlarr/Prowlarr/pull/2017

[Gauvino]

If I do all the change for lidarr readarr and whisparr, will you check to try switching to net8 ?

@bakerboy448