internal/core/adt: fix counter issue

Descendent fields of disjunct nodes may be marked
completed when they still will be forked into another
disjunction. This may lead to a zero counter to be
incremented.

We disable counter checking when breaking arc
depdencies within disjuncts to circumvent this.
Note that this may lead to some closedness errors
not being caught. As we want to simplify the closedness
rules this is probably good enough for now. Note
that this would mean that disjuncts get selected
based on closedness in the precense of breakable
parent-child cycles.

Closes #3750

Signed-off-by: Marcel van Lohuizen <[email protected]>
Change-Id: Ie4e630969221c5f181883873349fb8c0c15a2753
Reviewed-on: https://review.gerrithub.io/c/cue-lang/cue/+/1209299
TryBot-Result: CUEcueckoo <[email protected]>
Reviewed-by: Daniel Martí <[email protected]>
Unity-Result: CUE porcuepine <[email protected]>

Author: mpvl