Bump to Go 1.23

[sbueringer]

Once Kubernetes bumped to Go 1.23 we should also bump to Go 1.23 in Cluster API.

Tasks:

• Check if there is anything new in Go 1.23 that we have to adapt to
• Bump to Go 1.23 on main (this is done as part of the controller-runtime bump)
• Bump to Go 1.23 on release branches (this is done once k/k bumps on release branches)

k/k issue: kubernetes/release#3650

[sbueringer]

/area release
/triage accepted
/priority important-soon