Mark samAccountName generation as non-experimental

[lfrancke]

In SDP 24.11 we introduced the possibility to generate samAccountNames automatically
It's been used since then and we haven't seen any problems. Therefore we'd like to mark it as not-experimental anymore.

• Update documentation
• Update CRD to not have the experimental prefix anymore - potentially use CRD versioning for this?
• Add release notes and mention breaking change

[lfrancke]

We'll do #626 first to lay the groundwork. Once that is done this one should be simple.

[Techassi]

We decided to tackle this first (contrary to the comment above), because the change is slightly easier.