Allow to move products to other organizations

[sschuberth]

Similar to like we can already move repositories to other products / organizations, also whole products (incl. all their repositories) should be movable to other organizations.

[Etsija]

This is not a low-hanging fruit for the UI only: see the discussion in #4367 and the corresponding back-end PR #4417. The consequences of moving a product to a different organization would be also more severe than they were for moving a repository to another product: all user access rights from the product to be moved would probably have to be deleted, if I'm following the discussion in #4367 correctly.