structuredClone reads user-overridden RegExp properties

Description

The React Native structuredClone polyfill reads value.source and value.flags, so own overrides replace a RegExp's internal pattern/flags while cloning. Capturing only the aggregate flags getter is also insufficient because it reads user-visible per-flag properties such as global.

Expected behavior

RegExp cloning should read the built-in internal source and canonical d g i m s u v y flags without invoking or trusting own overrides, matching native structuredClone.

React Native Version

0.87.1 and current main

Affected Platforms

JavaScript runtime - All

从 React Native structuredClone polyfill 的入口点开始，检查其对 RegExp 的处理。为 source、flags 以及各个 flag 属性的自有覆盖添加回归测试覆盖，然后运行相关的 structuredClone 测试。当 RegExp 克隆使用内置 pattern 和规范化 flags，且不调用用户覆盖时，即视为完成。