Thread UTF-16 string input through JSON, script parsing, Date parsing,
Intl option parsing, Temporal parsing, and the helper library boundaries
that feed those parsers. Preserve ASCII fast paths where the source data
is known to be ASCII.
Inline JS-to-JS frames no longer live in the raw execution context
vector, so LibWeb callers that need to inspect or pop contexts now go
through VM helpers instead of peeking into that storage directly.
This keeps the execution context bookkeeping encapsulated while
preserving existing microtask and realm-entry checks.
Split JS::ErrorData out of JS::Error so that it can be used both
by JS::Error and WebIDL::DOMException. This adds support for
Error.isError to DOMException, also letting us report DOMException
stack information to the console.
