Use the `%target-swift-5.X-abi-triple` substitutions to compile the tests for
deployment to the minimum OS versions required for the APIs used in the tests,
instead of disabling availability checking.
The resignID call within the initializer moved into DI, because an assignment to
the actorSystem, and thus initialization of the id, is no longer guaranteed to happen.
Thus, while we previously could model the resignation as a clean-up emitted on all
unwind paths in an initializer, now it's conditional, based on whether the id was
initialized. This is exactly what DI is designed to do, so we inject the resignation
call just before we call the identity's deinit.
