internal/core/adt: add tests for Issue 3535

The issue was already fixed in CL 1203000.

Also add check to detect when a not allowed error
is created for a field type that is always allowed.

Create variants for various field types. Only the
one with the regular field should fail.

Fixes #3535

Signed-off-by: Marcel van Lohuizen <[email protected]>
Change-Id: Ib29dc3234ffd0a9adea8e7a9c45c90c012ac2506
Reviewed-on: https://review.gerrithub.io/c/cue-lang/cue/+/1203023
Reviewed-by: Daniel Martí <[email protected]>
Unity-Result: CUE porcuepine <[email protected]>
TryBot-Result: CUEcueckoo <[email protected]>

Author: mpvl