builtins: add ulid functionality

PR: https://github.com/cockroachdb/cockroach/pull/62440

From release notes:
> The `gen_ulid` and `uuid_ulid_to_string` [builtins](../v21.2/functions-and-operators.html#built-in-functions) are now available for use. [#62440][#62440] {% comment %}doc{% endcomment %}