Splash screen notification text:
- When starting in "Offline mode" with repositories with installed
packages enabled, the text is clickable unless launched with
`--offline-mode`, the tooltip notes that the command line setting
can't be changed at run-time.
- Don's show anything if there are not extensions installed.
Preferences:
- Don't show the welcome message on preferences if:
- Blender is online.
- The message was dismissed.
- There are no enabled remote repositories.
- The option to enable extensions.blender.org has been replaced with
a button that switches to the "System" tab where Online Access
can be enabled.
Also expose bpy.app.online_access_override needed for the UI to check
if online access was disabled using command line arguments.
4f73df2b7b