internal/core/adt: add benchmark for Issue 3334

This benchmark does not cover all problems related
to this issue, but covers the one that are not covered
well by current benchmarks and tests.

The main point her is to have a single disjunction
that dominates evaluation (complicating
memory management), where missing
(fine-grained) structure sharing becomes
critical.

We used CUE_UPDATE=force for this file to include
counters, which otherwise would not yet be triggered.

Issue #3334

Signed-off-by: Marcel van Lohuizen <[email protected]>
Change-Id: Ia1cd3f625ea47ba28111ea1dd06e967bf2a784aa
Reviewed-on: https://review.gerrithub.io/c/cue-lang/cue/+/1218175
Unity-Result: CUE porcuepine <[email protected]>
Reviewed-by: Daniel Martí <[email protected]>
TryBot-Result: CUEcueckoo <[email protected]>

Author: mpvl