Enable -Wexit-time-destructors for all in-tree library targets and
update process-lifetime library statics so they no longer register
exit-time destructors. Long-lived caches, lookup tables, singleton
registries, and generated constants now use NeverDestroyed or leaked
references where the data is intended to live until process exit.
Update LibWeb, LibLine, and the binding generators so regenerated
sources follow the same rule instead of reintroducing destructed
statics.
Some callers need the raw nul-terminated c-string in this callback, to
pass to some other ICU method. But other callers will want a StringView.
We know the length already in `icu_string_enumeration_to_list`, so let's
just pass it along to avoid `strlen`.
We were manually doing this for the calendar keyword, and would need to
do so for the collation keyword as well. I wasn't aware of this API
originally, so let's start using it.
