feat(clone): add structuredClone support for Error objects and relate…

[akshatnathani]

This Pull Request fixes/closes #5279.

It changes the following:

• Added Error object support in the JsValueStore serialization path so structuredClone(new Error("boom")) and postMessage(new Error("boom")) no longer fail during cloning.
• Implemented Error object reconstruction in the deserialization path using stored error metadata (kind, name, message, and related fields), instead of returning Not yet implemented.
• Added regression tests for both clone paths:
  • clone::tests::clones_error_objects
  • message::tests::basic_error_message
• Removed the stale #[expect(unused)] on the ValueStoreInner::Error variant, since it is now actively used.
• Verified consistency with project standards and checks:
  • cargo fmt --all -- --check
  • cargo clippy -p boa_runtime --tests -- -D warnings
  • cargo test -p boa_runtime clones_error_objects -- --nocapture
  • cargo test -p boa_runtime basic_error_message -- --nocapture

[jedel1043]

Looks good! I just have a couple of suggestions to improve the code.

[jedel1043]

This should be infallible, since we know original is already an Error type.
What we should do here is to add a conversion from JsObject<Error> to JsNativeError directly, and pass JsObject<Error> as our original object.

[jedel1043]

This looks kinda unmaintainable; you cannot easily distinguish which field is the name, the message, the stack or the cause at first glance. A proper struct would be better to make it harder to pass the incorrect field.