GitHub importer use default project visibility for non-private projects

What does this MR do?

GitHub importer use the Default Project Visibility setting for all non-private projects.

Why was this MR needed?

This allow users to import projects when Public visibility is restricted.

What are the relevant issue numbers?

Fixes #21437 (closed)

Does this MR meet the acceptance criteria?

• CHANGELOG entry added
• Tests
  • Added for this feature/bug
  • All builds are passing
• Conform by the style guides
• Branch has no merge conflicts with master (if you do - rebase it please)
• Squashed related commits together