_toExpr does not work for quantifiers in JS bindings

[NikolajBjorner]

The _toExpr coercion is necessary for using the high-level JS bindings.
It is currently not implemented for quantifiers.

z3/src/api/js/src/high-level/high-level.ts

Line 226 in ea8b118

if (kind === Z3_ast_kind.Z3_QUANTIFIER_AST) {

forall and exists quantifiers should be BoolImpl, otherwise assertions for Z3.And and similar operators fail.
lambda expressions have array sorts so they end up being ExprImpl.

@ritave

demo using JS bindings in the works: https://microsoft.github.io/z3guide/programming/Z3%20JavaScript%20Examples