ci: bump to ubuntu-24.04

[crazy-max]

relates to #3040 (comment)

[crazy-max]

Now I remember why we were still on ubuntu-20.04 for e2e tests. That's because k3s is not working since 22.04: https://github.com/docker/buildx/actions/runs/13658745854/job/38184705379#step:7:86

/usr/bin/kubectl get nodes --no-headers -oname
E0304 16:53:48.732555    2194 memcache.go:265] "Unhandled Error" err="couldn't get current server API group list: Get \"https://127.0.0.1:6443/api?timeout=32s\": dial tcp 127.0.0.1:6443: connect: connection refused"
E0304 16:53:48.733923    2194 memcache.go:265] "Unhandled Error" err="couldn't get current server API group list: Get \"https://127.0.0.1:6443/api?timeout=32s\": dial tcp 127.0.0.1:6443: connect: connection refused"
E0304 16:53:48.735196    2194 memcache.go:265] "Unhandled Error" err="couldn't get current server API group list: Get \"https://127.0.0.1:6443/api?timeout=32s\": dial tcp 127.0.0.1:6443: connect: connection refused"
E0304 16:53:48.736490    2194 memcache.go:265] "Unhandled Error" err="couldn't get current server API group list: Get \"https://127.0.0.1:6443/api?timeout=32s\": dial tcp 127.0.0.1:6443: connect: connection refused"
E0304 16:53:48.737814    2194 memcache.go:265] "Unhandled Error" err="couldn't get current server API group list: Get \"https://127.0.0.1:6443/api?timeout=32s\": dial tcp 127.0.0.1:6443: connect: connection refused"
The connection to the server 127.0.0.1:6443 was refused - did you specify the right host or port?
Unable to resolve node name (The process '/usr/bin/kubectl' failed with exit code 1). Attempt 1 of 10.

I will try to fix that but we could disable kubernetes tests in the meantime.

[crazy-max]

Pushed extra commit to fix k3s install. See upstream change: crazy-max/.github#27