Update configurator python code to be more robust when specifying the duplicate namelist property

### Are there any linked Issues or Pull Requests?

_No response_

### Brief description

When generating **config_mod.f90** which defines the **config_type** for an application, a list of booleans is passed which indicates which namelists are allowed to have duplicates (multiple instances). The ordering is important which makes the usage fragile.

It's low risk as, it is not likely to be used manually except by developers, though this issue is to make the process generally more robust.

### Further details of the issue.

_No response_