add support for resolveManyEntities to return a list of entities and errors

When using `resolveEntity`, then `resolveEntityGroup` populates the response with either an entity or an error, depending on what the resolver returns.

With `resolveManyEntities`, the plugin takes either the list of entities, or the errors; it would be nice to be able to return a mix of entities AND errors, like the end user would get in case `resolveEntity` is being used.

If you don't want to support it out-of-the-box, it would be nice if you could provide an option to override the federation template, then we would be able to customize it to our use case.

查看 federation 插件的代码（可能位于 plugin/federation），以了解 resolveManyEntities 当前的工作方式。检查 federation resolver 的模板生成。目标是修改该插件，使其能够返回实体和错误的混合结果，类似于 resolveEntity。检查 federation 的现有测试，了解如何验证该行为。

由索引模型根据 Issue 内容生成。