Consolidate and settle on Ubuntu version

[n1koo]

Currently both on CI and in our documentation we reference various versions of Ubuntu (22.04, 20.04 and latest).

24.04 LTS will be released soon'ish and lets fix all references to that when its out.

This will allow a very long term support without touching the OS version again

[rikukissa]

Some existing documentation here: https://app.gitbook.com/o/zub8C4BetmW3a9Bj4Cd4/s/TpMZa3OhuU8OphPGJLBn/servers/upgrading-eol-ubuntu

[n1koo]

Seems like Github folks lag behind pretty badly on releases actions/runner-images#9691 (comment)

For short term i'll lock us to 22.04 on everything

[n1koo]

Closing this off as we did 22.04 where we could - #7045 should follow for the upgrade of all-things