swift

358869ff - [Concurrency] NonisolatedNonsendingByDefault: Extend `nonisolated(nonsending)` to `_openExistential`

[Concurrency] NonisolatedNonsendingByDefault: Extend `nonisolated(nonsending)` to `_openExistential` `_openExistential` is type-checked in a special way which means that we need to explicitly inject `nonisolated(nonsending)` isolation when forming a reference to this builtin.