New test case: Variant of T14052 with data type definitions

previous attempts at #11547 (closed) and #20455 (closed) were reverted because th showed some quadratic behavior, and the test case T15052 was added to catch that.

I believe that similar quadratic behavior can be triggered with current master, by using type definitions rather than value definitions, so th adds a test case similar to T14052. I have hopes that my attempts at #20455 (closed) will lead to code that avoid the quadratic increase here Or not, we will see. In any case, having this in master and included in future comparisons will be useful.