Test consistency between "raw_elements" and regular "fields"

[matz-e]

We could implement the following consistency check. For every type of circuit, perform two queries:

1. Use fields="raw_elements"
2. Use fields=... a regular 'builtin' field

Then check that the returned values are the same. This transfers correctness of builtin fields to "raw_elements", i.e. if we test the builtin fields thoroughly we get "raw_elements" for free; and ensures that everything looks consistent.