Implement Postal Code Generator using Positional Generator for locale `nl`

[thdaraujo]

In lib/locales/nl.yml, there is a very large definition for a generator with over 2000 characters to be used by the regexify method.

My understanding, based on this discussion is that any combination of 2 uppercase characters are valid, except for SA, SS, and SD.

Instead of implementing a way to exclude the invalid combinations, the locale specifies all the 673 repeated permutations of possible 2-letter words that are valid. This seems very excessive to me.

AA, AB, AC, ... ZZ.

I think we could simply implement this with a generator for the postal code excluding using the positional generator instead.

[stefannibrasil]

faker japanese has more than 120k values for postcode 🤯 https://github.com/faker-ruby/faker/blob/2258715a7b2b2cf8dc680abb57eea6eeac81651a/lib/locales/ja/address.yml