Rework notification providers

[bastimeyer]

Meta thread for the following tasks:

• Rename native provider to chromium
• Fix notifications on Windows
  Launched streams and ToastNotifications created by Twitch GUI create unusual windows wait cursor behaviour. #952 (comment)
  • Replace snoretoast with chromium provider
  • Remove rich provider
• Re-implement freedesktop notifications via custom dbus implementation
  Re-implement freedesktop notifications via custom dbus implementation #959
• Remove growl provider