Restored pagination on namespace combo + removed not relevant `pageSize` attributes from some combos

### What does it do ?

Removes unnecessary `pageSize` attributes from some combo box to prevent misunderstanding (processors were not using them) +
Restored pagination on namespace combo box.

### Why is it needed ?

If you have more than 20 namespaces, you are not able to access the 20+ ones (unless you use the type ahead feature)