Keep a numeric TS enum's reverse-mapping keys out of `.options` (#6542)

`z.enum()` accepts a TypeScript enum, whose runtime object carries both
directions of the mapping. The parse set already drops the reverse half via
`util.getEnumValues`, but `.options` was assigned straight from
`Object.values(def.entries)`, so a three-member numeric enum reported six
options — three of which `.parse()` rejects, and none of which its declared
`Array<T[keyof T]>` type admits.

Assign from the value set core already built instead. Classic and mini both
carried the line.