This will make it easier to support both string types at the same time
while we convert code, and tracking down remaining uses.
One big exception is Value::to_string() in LibJS, where the name is
dictated by the ToString AO.
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 runtime environment of the WASM REPL does not have time zone
information; the file system is virtual (does not have /etc/localtime),
and the TZ environment variable is not set. This causes LibTimeZone to
always fall back to UTC.
Instead, we can get the time zone from the user's browser before we
enter this limited environment. The REPL website will pass the time zone
into the WASM REPL.
