These tests are easier to write and maintain if the grammars are just JS,
like grammars normally are. It doesn't slow the tests down significantly
to shell out to `node` for each of these grammars.
We previously maintained a set of individual productions that were
involved in conflicts, but that was subtly incorrect because
we don't compare productions themselves when comparing parse items;
we only compare the parse items properties that could affect the
final reduce actions.
