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.
Shared workers are essentially just workers that may be accessed from
scripts within the same origin. There are plenty of FIXMEs here (mostly
building on existing worker FIXMEs that are already in place), but this
lets us run the shared worker variants of WPT tests.