- reuse more code about getting the type and requirements
- handle protocols properly, including extensions with where clauses
- improve error messages
* [Distributed] towards DistributedActorSystem; synthesize the id earlier, since Identifiable.id
* Fix execute signature to what Pavel is working with
* funcs are ok in sil
* fixed lifetime of id in inits
* fix distributed_actor_deinit
* distributed_actor_local
* update more tests
fixing tests
fix TBD test
fix Serialization/distributed
fix irgen test
Fix null pointer crashes
* prevent issues with null func ptrs and fix Distributed prorotocol test
* fix deinit sil test
The _Distributed module is being introduced in Swift 5.6, so its definitions need to come with matching availability. (We don't have version numbers for the associated OS releases, so we need to use placeholder 9999 availability for these.)
The concurrency runtime now deploys back to macOS 10.15, iOS 13.0, watchOS 6.0, tvOS 13.0, which corresponds to the 5.1 release of the stdlib.
Adjust macro usages accordingly.
Remove a few places where we are introducing extra distributed-related
actor isolation checking that either isn't necesssary or is incorrect.
Specifically:
* Hopping to a global actor *from* a distributed-actor isolated context
does not go through a distributed thunk (global actors can't have one).
* "Unrestricted" declarations are always unrestricted, so we don't
need an extra distributed check here (it won't ever occur).
* Actor isolation computation doesn't need a special case for
distributed; it marks too much, overriding (e.g.) global actor
isolation.
The primary semantic change visible here is that distributed actors
can now have truly 'nonisolated' members. They aren't required to be
'distributed' because they can't touch state anyway.
