[Select] Customize placeholder

[jeremie-lucca]

Intention

In some cases it would be useful to customize placeholder the same way we allow to customize displayer:

https://github.com/user-attachments/assets/58944ff7-1ded-4c10-9ef1-ef617393647c

Key points

Mistakes to avoid

[fbasmaison-lucca]

Another way of tackling our current issue would be to add prefix or suffix to the select.

[Supamiu]

Yeah I feel like having a prefix might be a better solution.