Switch to Yocto 5.0 (LTS)

[KanjiMonster]

Yocto 5.0 (Scarthgap) is planned to be the next LTS release, and is planned for April 24. To keep up to date, we should work on switching to it once it nears the release.

• Yocto 5.0 released
• convert templateconf.cfg to a proper configuration template
• update our recipes/code to work with usrmerge¹
• update meta-open-network-linux to scarthgap
• update meta-switch to scarthgap
• update meta-ofdpa to scarthgap
• update meta-ofdpa-closed to scarthgap
• decide on the fate of ryu (os-ken)
• switch to Yocto 5.0
• verify everything works

¹ usrmerge means there is no separate /bin,/lib etc anymore, and everything is now in /usr.

[KanjiMonster]

Yocto 5.0 is out, so we could switch at any time*

[KanjiMonster]

Yocto 5.0 will require reorganization of our repository, so let's wait for after 5.2 with this.

[KanjiMonster]

Most things build with minor changes.

Biggest blocker will be ryu, which uses easy_install from python3's setuptools, which is deprecated and the parts that ryu uses were already removed, so it currently fails to build. Fixing this is a non-trivial change, so we need to discuss if we want to spend the effort, or just drop ryu in 6.0, unless there are customers requiring it.

Os-ken currently has the same issue, so it isn't an alternative, though the likelyhood of it being changed there is higher, as it is actually maintained.