Use openSUSE-repos for repo definitions on both Leap16 and Tumbleweed

[lkocman]

Use openSUSE-repos for repo definitions on systems deployed by agama

• Avoid default installation on all systems by not adding it to patterns and add it to mandatory packages instead\

I do have agreement with @DimStar77 to get Agama early-adopters test openSUSE-repos before it hits Leap 16, hopefully as default just like in Leap Micro 6.0. It will help me with migration.

This would significally help with testing of https://news.opensuse.org/2023/07/31/try-out-cdn-with-opensuse-repos/

[imobachgs]

Thanks!