Instead, use the `%target-swift-5.1-abi-triple` substitution to compile the tests
for deployment to the minimum OS versions required for use of _Concurrency APIs.
This means that:
1. In test cases where minimal is the default (swift 5 without
-warn-concurrency), I added RUN lines for targeted, complete, and complete +
sns.
2. In test cases where complete is the default (swift 6, -warn-concurrency,
specified complete with -strict-concurrency), I added a send non-sendable run
line.
In each of these cases, I added additional expected-* lines as appropriate so
the tests can compile in each mode successfully.
This fixes a performance regression with the reasync '&&', '||' and '??'
operators.
Also arguably it makes sense anyway since 'reasync' functions can in
fact be called from synchronous functions, so the solution should not
be considered worse.
We don't actually want to be able to overload a synchronous function
with a 'reasync' function anyway; the whole point of 'reasync' is to
avoid the need for such overloading.
Fixes rdar://problem/76254445.
