Find all the usages of `--enable-experimental-feature` or
`--enable-upcoming-feature` in the tests and replace some of the
`REQUIRES: asserts` to use `REQUIRES: swift-feature-Foo` instead, which
should correctly apply to depending on the asserts/noasserts mode of the
toolchain for each feature.
Remove some comments that talked about enabling asserts since they don't
apply anymore (but I might had miss some).
All this was done with an automated script, so some formatting weirdness
might happen, but I hope I fixed most of those.
There might be some tests that were `REQUIRES: asserts` that might run
in `noasserts` toolchains now. This will normally be because their
feature went from experimental to upcoming/base and the tests were not
updated.
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.
With the introduction of `next(isolation:)` into the task group types,
we removed the public APIs for the no-argument `next()` versions,
leaving them only as `@usableFromInline internal` entrypoints for the
ABI. Because the `next(isolation:)` versions have a default argument,
this was sufficient for providing source compatibility for calls, but
not for protocol conformances.
Bring these APIs back publicly. Fixes rdar://127499568.
