Ignore RegExp property overrides when cloning

[OskarEichler]

Summary:

The structured-clone polyfill reads user-visible RegExp source/flags, allowing own overrides to replace internal state. Capture and call the built-in source and individual flag getters, feature-detecting d/v, and construct canonical dgimsuvy flags directly from internal slots.

Fixes #58224.

Changelog:

[GENERAL] [FIXED] - Clone RegExp internal source and flags without using property overrides.

Test Plan:

• Exact Hermes baseline cloned internal /foo/g with shadowed properties as /bar/.
• Final regression shadows source, aggregate flags, and every individual flag property with conflicting values; the clone remains /foo/g.
• Fixed focused Fantom suite: 32/32 passed, matching native structuredClone.
• Fresh yarn flow-check: 0 errors.
• Targeted ESLint, Prettier, and git diff --check passed.

Root review caught that the first draft's captured aggregate flags getter still read per-flag overrides; the final head uses the individual intrinsics. No UI change; screenshots are not applicable.