With the GC heap conversion, the functionality of legacy platform
objects was broken. This is because the generated implementation of one
of them was used for all of them, removing functionality such as
deletion.
This re-adds all functionality, where questions such as "does the
object support indexed properties?" is instead answered by virtual
functions instead of by the IDL generator checking the presence of
certain keywords/attributes.
DeprecatedFlyString relies heavily on DeprecatedString's StringImpl, so
let's rename it to A) match the name of DeprecatedString, B) write a new
FlyString class that is tied to String.
Note that js_rope_string() has been folded into this, the old name was
misleading - it would not always create a rope string, only if both
sides are not empty strings. Use a three-argument create() overload
instead.
We have a new, improved string type coming up in AK (OOM aware, no null
state), and while it's going to use UTF-8, the name UTF8String is a
mouthful - so let's free up the String name by renaming the existing
class.
Making the old one have an annoying name will hopefully also help with
quick adoption :^)
The combination of template + auto&& parameter + constexpr if statements
allowed one caller to pass in a GlobalObject, without the compiler
complaining.
This will be inherited by "legacy platform objects", i.e objects that
need to hijack indexed and/or named property access as described in the
IDL spec: https://webidl.spec.whatwg.org/#dfn-legacy-platform-object
Instead of overriding JS::Object virtuals, subclasses only need to
implement a very simple interface for property queries.
Note that this code is taken verbatim from code generator output.
I didn't write any of this now, so it's effectively "moved" code.
