[prisma] Using extensions to remove the need for `subject` helper with prisma

Is your feature request related to a problem? Please describe. Currently, you need the subject helper to use CASL with Prisma. With client extensions being stable now, we can do better.

Describe the solution you'd like Provide a pre-packaged extension in CASL, that will add the model name to a field in prisma client (maybe use a symbol for the field?). Make the default detectSubjectType know how to read that field.

Describe alternatives you've considered This is fairly easily solvable in user-land, just thought it might be a good idea if the prisma package made the process streamlined.