refactor(zod/v4): use .superRefine() for externals

[colinaaa]

Summary

Replace ZodRspackCrossChecker with .superRefine() (renamed to .check() in Zod v4) for umd external object (introduced in #8369).

The ZodRspackCrossChecker relies on internal methods of ZodType, such as _getOrReturnCtx and _getRootData, which are no longer exists in Zod v4.

I couldn't find a way to get the parent schema in Zod v4, so I decided to directly make the check from root with .superRefine().

The similar changes would be made to builtin:swc-loader in the next PR.

issue: #10467

Checklist

• Tests updated (or not required).

I think we've got enough tests in #8369.

• Documentation updated (or not required).

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[codspeed-hq]

CodSpeed Performance Report

Merging #10609 will not alter performance

_{Comparing colinaaa:zod-v4 (b6f141c) with main (26b3e78)}

Summary

✅ 12 untouched benchmarks