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.
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 :^)
These classes only needed Window to get at its realm. Pass a realm
directly to construct Crypto, Encoding, HRT, IntersectionObserver,
NavigationTiming, Page, RequestIdleCallback, Selection, Streams, URL,
and XML classes.
This is a minor refactor of IDL::get_buffer_source_copy() letting it
return ErrorOr<ByteBuffer> instead of Optional<ByteBuffer>.
This also updates all places that use IDL::get_buffer_source_copy().
