Simplification: push negation into Case expression

Why would this be usefull?

• right now a boolean CASE expressions are translated into AND/ORs in most cases ; "disjunction of conjuctions"
• AND/OR simplification could "push" the NOT into them; but only after the CASE conversion; so the expression becames a "conjunction of disjunctions" and all the other simplification rules are working hard to restore order....
• if the push of NOT would happen earlier it would be better because it could address complex cases better

  @Test public void testNotIntoCase() {
    checkSimplify(
        not(
            case_(
                isTrue(vBool()), vBool(1),
                vBool(2))),
        "CASE(IS TRUE(?0.bool0), NOT(?0.bool1), NOT(?0.bool2))");
  }

actually NOT right now stops the simplification recursion so it would be best to also enable that as well; in case NOT is not is not pushed/handled - unknownAs need to be negated.

 @Test public void testNotRecursion() {
    checkSimplify(
        not(coalesce(nullBool, trueLiteral)),
        "false");
  }