I went through all callers of adopt_own() and replaced them with
try_make<>() if possible or adopt_nonnull_own_or_enomem() else
in cases where it was easy (i.e. in functions already returning
ErrorOr).
No intended behavior change.
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 :^)
