[Concurrency/Distributed] nonisolated-nonsending by default breaks distributed thunks
the new NonisolatedNonsendingByDefault upcoming feature breaks remote
calls in distributed actors, because the expected isolation doesn't
match and the runtime swift_distributed_execute_target_resume will
crash.
This is a short term fix to unblock adopters, however preferably we
should mark the thunks as nonisolated(nonsending), though that seems to
be more involved.
resolves rdar://159247975