Support Zod 3.21 & 3.22

The new version of Zod brings new schema features which will need corresponding support in zod-fast-check.

https://github.com/colinhacks/zod/releases/tag/v3.21

Features:
- [ ] `.emoji`
- [ ] `.cuid2`
- [ ] `.ip`
- [ ] `z.bigint().{gt|gte|lt|lte}()`
- [ ] `z.enum(...).extract()` and `z.enum(...).exclude()`
- [ ] `.ulid`
- [x] `.readonly`

Start with the linked Zod 3.21 release notes, then inspect zod-fast-check's current handling of the listed schema features. Support the unchecked items—.emoji, .cuid2, .ip, bigint comparisons, enum extraction and exclusion, and .ulid—and verify each item against the existing test suite.

Written by the indexing model from the issue text.